Added all files

26 files changed, 8190 insertions, 0 deletions

diff --git a/xlators/performance/Makefile.am b/xlators/performance/Makefile.am
new file mode 100644
index 00000000000..f7504bbe8f3
--- /dev/null
+++ b/xlators/performance/Makefile.am
@@ -0,0 +1,3 @@
+SUBDIRS = write-behind read-ahead io-threads io-cache symlink-cache
+
+CLEANFILES = 
diff --git a/xlators/performance/io-cache/Makefile.am b/xlators/performance/io-cache/Makefile.am
new file mode 100644
index 00000000000..d471a3f9243
--- /dev/null
+++ b/xlators/performance/io-cache/Makefile.am
@@ -0,0 +1,3 @@
+SUBDIRS = src
+
+CLEANFILES = 
diff --git a/xlators/performance/io-cache/src/Makefile.am b/xlators/performance/io-cache/src/Makefile.am
new file mode 100644
index 00000000000..b1bf5bfbf71
--- /dev/null
+++ b/xlators/performance/io-cache/src/Makefile.am
@@ -0,0 +1,14 @@
+xlator_LTLIBRARIES = io-cache.la
+xlatordir = $(libdir)/glusterfs/$(PACKAGE_VERSION)/xlator/performance
+
+io_cache_la_LDFLAGS = -module -avoidversion 
+
+io_cache_la_SOURCES = io-cache.c page.c ioc-inode.c
+io_cache_la_LIBADD = $(top_builddir)/libglusterfs/src/libglusterfs.la
+
+noinst_HEADERS = io-cache.h
+
+AM_CFLAGS = -fPIC -D_FILE_OFFSET_BITS=64 -D_GNU_SOURCE -Wall -D$(GF_HOST_OS) \
+	-I$(top_srcdir)/libglusterfs/src -shared -nostartfiles $(GF_CFLAGS)
+
+CLEANFILES = 
diff --git a/xlators/performance/io-cache/src/io-cache.c b/xlators/performance/io-cache/src/io-cache.c
new file mode 100644
index 00000000000..f367cdb88de
--- /dev/null
+++ b/xlators/performance/io-cache/src/io-cache.c
@@ -0,0 +1,1478 @@
+/*
+  Copyright (c) 2007, 2008, 2009 Z RESEARCH, Inc. <http://www.zresearch.com>
+  This file is part of GlusterFS.
+
+  GlusterFS is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published
+  by the Free Software Foundation; either version 3 of the License,
+  or (at your option) any later version.
+
+  GlusterFS is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see
+  <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef _CONFIG_H
+#define _CONFIG_H
+#include "config.h"
+#endif
+
+#include "glusterfs.h"
+#include "logging.h"
+#include "dict.h"
+#include "xlator.h"
+#include "io-cache.h"
+#include <assert.h>
+#include <sys/time.h>
+
+static uint32_t
+ioc_get_priority (ioc_table_t *table, 
+		  const char *path);
+
+static uint32_t
+ioc_get_priority (ioc_table_t *table, 
+		  const char *path);
+
+static inline ioc_inode_t *
+ioc_inode_reupdate (ioc_inode_t *ioc_inode)
+{
+	ioc_table_t *table = ioc_inode->table;
+
+	list_add_tail (&ioc_inode->inode_lru, 
+		       &table->inode_lru[ioc_inode->weight]);
+  
+	return ioc_inode;
+}
+
+static inline ioc_inode_t *
+ioc_get_inode (dict_t *dict,
+	       char *name)
+{
+	ioc_inode_t *ioc_inode = NULL;
+	data_t *ioc_inode_data = dict_get (dict, name);
+	ioc_table_t *table = NULL;
+
+	if (ioc_inode_data) {
+		ioc_inode = data_to_ptr (ioc_inode_data);
+		table = ioc_inode->table;
+
+		ioc_table_lock (table);
+		{
+			if (list_empty (&ioc_inode->inode_lru)) {
+				ioc_inode = ioc_inode_reupdate (ioc_inode);
+			}
+		}
+		ioc_table_unlock (table);
+	}
+  
+	return ioc_inode;
+}
+
+int32_t
+ioc_inode_need_revalidate (ioc_inode_t *ioc_inode)
+{
+	int8_t need_revalidate = 0;
+	struct timeval tv = {0,};
+	int32_t ret = -1;
+	ioc_table_t *table = ioc_inode->table;
+
+	ret = gettimeofday (&tv, NULL);
+
+	if (time_elapsed (&tv, &ioc_inode->tv) >= table->cache_timeout)
+		need_revalidate = 1;
+
+	return need_revalidate;
+}
+
+/*
+ * __ioc_inode_flush - flush all the cached pages of the given inode
+ *
+ * @ioc_inode: 
+ *
+ * assumes lock is held
+ */
+int32_t
+__ioc_inode_flush (ioc_inode_t *ioc_inode)
+{
+	ioc_page_t *curr = NULL, *next = NULL;
+	int32_t destroy_size = 0;
+	int32_t ret = 0;
+
+	list_for_each_entry_safe (curr, next, &ioc_inode->pages, pages) {
+		ret = ioc_page_destroy (curr);
+    
+		if (ret != -1) 
+			destroy_size += ret;
+	}
+  
+	return destroy_size;
+}
+
+void
+ioc_inode_flush (ioc_inode_t *ioc_inode)
+{
+	int32_t destroy_size = 0;    
+
+	ioc_inode_lock (ioc_inode);
+	{
+		destroy_size = __ioc_inode_flush (ioc_inode);
+	}
+	ioc_inode_unlock (ioc_inode);
+  
+	if (destroy_size) {
+		ioc_table_lock (ioc_inode->table);
+		{
+			ioc_inode->table->cache_used -= destroy_size;
+		}
+		ioc_table_unlock (ioc_inode->table);
+	}
+
+	return;
+}
+
+/* 
+ * ioc_utimens_cbk -
+ * 
+ * @frame:
+ * @cookie:
+ * @this:
+ * @op_ret:
+ * @op_errno:
+ * @stbuf:
+ *
+ */
+int32_t
+ioc_utimens_cbk (call_frame_t *frame,
+		 void *cookie,
+		 xlator_t *this,
+		 int32_t op_ret,
+		 int32_t op_errno,
+		 struct stat *stbuf)
+{
+	STACK_UNWIND (frame, op_ret, op_errno, stbuf);
+	return 0;
+}
+
+/* 
+ * ioc_utimens -
+ * 
+ * @frame:
+ * @this:
+ * @loc:
+ * @tv:
+ *
+ */
+int32_t
+ioc_utimens (call_frame_t *frame,
+	     xlator_t *this,
+	     loc_t *loc,
+	     struct timespec *tv)
+{
+	uint64_t ioc_inode = 0;
+	inode_ctx_get (loc->inode, this, &ioc_inode);
+
+	if (ioc_inode)
+		ioc_inode_flush ((ioc_inode_t *)(long)ioc_inode);
+
+	STACK_WIND (frame, ioc_utimens_cbk,
+		    FIRST_CHILD (this),
+		    FIRST_CHILD (this)->fops->utimens,
+		    loc, tv);
+	return 0;
+}
+
+int32_t
+ioc_lookup_cbk (call_frame_t *frame,
+		void *cookie,
+		xlator_t *this,
+		int32_t op_ret,
+		int32_t op_errno,
+		inode_t *inode,
+		struct stat *stbuf,
+		dict_t *dict)
+{
+	ioc_inode_t *ioc_inode = NULL;
+	ioc_local_t *local = frame->local;
+	ioc_table_t *table = this->private;
+	ioc_page_t  *page = NULL;
+	data_t      *page_data = NULL;
+	data_t      *content_data = NULL;
+	char        *src = NULL;
+	char        *dst = NULL;
+	char         need_unref = 0;
+	uint8_t      cache_still_valid = 0;
+	uint32_t     weight = 0;
+	uint64_t     tmp_ioc_inode = 0;
+	char        *buf = NULL;
+	char        *tmp = NULL;
+	int          i;
+	
+	if (op_ret != 0) 
+		goto out;
+
+	inode_ctx_get (inode, this, &tmp_ioc_inode);
+	ioc_inode = (ioc_inode_t *)(long)tmp_ioc_inode;
+	if (ioc_inode) {
+		cache_still_valid = ioc_cache_still_valid (ioc_inode, 
+							   stbuf);
+		
+		if (!cache_still_valid) {
+			ioc_inode_flush (ioc_inode);
+		} 
+		/* update the time-stamp of revalidation */
+		ioc_inode_lock (ioc_inode);
+		{
+			gettimeofday (&ioc_inode->tv, NULL);
+		}
+		ioc_inode_unlock (ioc_inode);
+		
+		ioc_table_lock (ioc_inode->table);
+		{
+			list_move_tail (&ioc_inode->inode_lru,
+					&table->inode_lru[ioc_inode->weight]);
+		}
+		ioc_table_unlock (ioc_inode->table);
+	}
+	
+	if (local && stbuf->st_size && 
+	    local->need_xattr >= stbuf->st_size) {
+		if (!ioc_inode) {
+			weight = ioc_get_priority (table, 
+						   local->file_loc.path);
+			ioc_inode = ioc_inode_update (table, 
+						      inode, weight);
+			inode_ctx_put (inode, this, 
+				       (uint64_t)(long)ioc_inode);
+		}
+		
+		ioc_inode_lock (ioc_inode);
+		{
+			content_data = dict_get (dict, "glusterfs.content");
+			page = ioc_page_get (ioc_inode, 0);
+			
+			if (content_data) {
+				if (page) {
+					dict_unref (page->ref);
+					free (page->vector);
+					page->vector = NULL;
+					
+					ioc_table_lock (table);
+					{
+						table->cache_used -= 
+							page->size;
+					}
+					ioc_table_unlock (table);
+				} else {
+					page = ioc_page_create (ioc_inode, 0);
+				}
+				
+				dst = CALLOC (1, stbuf->st_size);
+				page->ref = dict_ref (get_new_dict ());
+				page_data = data_from_dynptr (dst, 
+							      stbuf->st_size);
+				dict_set (page->ref, NULL, page_data);
+				
+				src = data_to_ptr (content_data);
+				memcpy (dst, src, stbuf->st_size);
+
+				page->vector = CALLOC (1, 
+						       sizeof (*page->vector));
+				page->vector->iov_base = dst;
+				page->vector->iov_len = stbuf->st_size;
+				page->count = 1;
+      
+				page->waitq = NULL;
+				page->size = stbuf->st_size;
+				page->ready = 1;
+
+				ioc_table_lock (table);
+				{
+					table->cache_used += page->size;
+				}
+				ioc_table_unlock (table);
+				
+			} else {
+				if (!(page && page->ready)) {
+					gf_log (this->name, GF_LOG_DEBUG,
+						"page not present");
+					
+					ioc_inode_unlock (ioc_inode);
+					STACK_WIND (frame,
+						    ioc_lookup_cbk,
+						    FIRST_CHILD (this),
+						    FIRST_CHILD (this)->fops->lookup,
+						    &local->file_loc,
+						    local->xattr_req);
+					return 0;
+				} 
+				buf = CALLOC (1, stbuf->st_size);
+				tmp = buf;
+
+				for (i = 0; i < page->count; i++) {
+					memcpy (tmp, page->vector[i].iov_base, 
+						page->vector[i].iov_len);
+					tmp += page->vector[i].iov_len;
+				}
+				
+				gf_log (this->name, GF_LOG_DEBUG,
+					"serving file %s from cache", 
+					local->file_loc.path);
+				
+				if (!dict) {
+					need_unref = 1;
+					dict = dict_ref (
+						get_new_dict ());
+				}
+				dict_set (dict, "glusterfs.content",
+					  data_from_dynptr (buf, 
+							    stbuf->st_size));
+			}
+
+			ioc_inode->mtime = stbuf->st_mtime;
+			gettimeofday (&ioc_inode->tv, NULL);
+		}
+		ioc_inode_unlock (ioc_inode);
+		
+		if (content_data && 
+		    ioc_need_prune (ioc_inode->table)) {
+			ioc_prune (ioc_inode->table);
+		}
+	}
+
+ out:
+	STACK_UNWIND (frame, op_ret, op_errno, inode, stbuf, dict);
+
+	if (need_unref) {
+		dict_unref (dict);
+	}
+
+	return 0;
+}
+
+int32_t 
+ioc_lookup (call_frame_t *frame,
+	    xlator_t *this,
+	    loc_t *loc,
+	    dict_t *xattr_req)
+{
+	uint64_t content_limit = 0;
+
+	if (GF_FILE_CONTENT_REQUESTED(xattr_req, &content_limit)) {
+		uint64_t     tmp_ioc_inode = 0;
+		ioc_inode_t *ioc_inode = NULL;
+		ioc_page_t  *page = NULL;
+		ioc_local_t *local = CALLOC (1, sizeof (*local));
+
+		local->need_xattr = content_limit;
+		local->file_loc.path = loc->path;
+		local->file_loc.inode = loc->inode;
+		frame->local = local;
+
+		inode_ctx_get (loc->inode, this, &tmp_ioc_inode);
+		ioc_inode = (ioc_inode_t *)(long)tmp_ioc_inode;
+
+		if (ioc_inode) {
+			ioc_inode_lock (ioc_inode);
+			{
+				page = ioc_page_get (ioc_inode, 0);
+				if ((content_limit <= 
+				     ioc_inode->table->page_size) && 
+				    page && page->ready) {
+					local->need_xattr = -1;
+				}
+			}
+			ioc_inode_unlock (ioc_inode);
+		}
+	}
+
+	STACK_WIND (frame,
+		    ioc_lookup_cbk,
+		    FIRST_CHILD (this),
+		    FIRST_CHILD (this)->fops->lookup,
+		    loc,
+		    xattr_req);
+	return 0;
+}
+
+/*
+ * ioc_forget - 
+ *
+ * @frame:
+ * @this:
+ * @inode:
+ *
+ */
+int32_t
+ioc_forget (xlator_t *this,
+	    inode_t *inode)
+{
+	uint64_t ioc_inode = 0;
+
+	inode_ctx_get (inode, this, &ioc_inode);
+
+	if (ioc_inode)
+		ioc_inode_destroy ((ioc_inode_t *)(long)ioc_inode);
+	    
+	return 0;
+}
+
+
+/* 
+ * ioc_cache_validate_cbk - 
+ *
+ * @frame:
+ * @cookie:
+ * @this:
+ * @op_ret:
+ * @op_errno:
+ * @buf
+ *
+ */
+int32_t
+ioc_cache_validate_cbk (call_frame_t *frame,
+			void *cookie,
+			xlator_t *this,
+			int32_t op_ret,
+			int32_t op_errno,
+			struct stat *stbuf)
+{
+	ioc_local_t *local = frame->local;
+	ioc_inode_t *ioc_inode = NULL;
+	size_t destroy_size = 0;
+	struct stat *local_stbuf = stbuf;
+
+	ioc_inode = local->inode;
+
+	if ((op_ret == -1) || 
+	    ((op_ret >= 0) && !ioc_cache_still_valid(ioc_inode, stbuf))) {
+		gf_log (ioc_inode->table->xl->name, GF_LOG_DEBUG,
+			"cache for inode(%p) is invalid. flushing all pages",
+			ioc_inode);
+		/* NOTE: only pages with no waiting frames are flushed by 
+		 * ioc_inode_flush. page_fault will be generated for all 
+		 * the pages which have waiting frames by ioc_inode_wakeup()
+		 */
+		ioc_inode_lock (ioc_inode);
+		{
+			destroy_size = __ioc_inode_flush (ioc_inode);
+			if (op_ret >= 0)
+				ioc_inode->mtime = stbuf->st_mtime;
+		}
+		ioc_inode_unlock (ioc_inode);
+		local_stbuf = NULL;
+	}
+
+	if (destroy_size) {
+		ioc_table_lock (ioc_inode->table);
+		{
+			ioc_inode->table->cache_used -= destroy_size;
+		}
+		ioc_table_unlock (ioc_inode->table);
+	}
+
+	if (op_ret < 0)
+		local_stbuf = NULL;
+  
+	ioc_inode_lock (ioc_inode);
+	{
+		gettimeofday (&ioc_inode->tv, NULL);
+	}
+	ioc_inode_unlock (ioc_inode);
+
+	ioc_inode_wakeup (frame, ioc_inode, local_stbuf);
+  
+	/* any page-fault initiated by ioc_inode_wakeup() will have its own 
+	 * fd_ref on fd, safe to unref validate frame's private copy 
+	 */
+	fd_unref (local->fd);
+
+	STACK_DESTROY (frame->root);
+
+	return 0;
+}
+
+static int32_t
+ioc_wait_on_inode (ioc_inode_t *ioc_inode, 
+		   ioc_page_t *page)
+{
+	ioc_waitq_t *waiter = NULL, *trav = NULL;
+	uint32_t page_found = 0;
+
+	trav = ioc_inode->waitq;
+
+	while (trav) {
+		if (trav->data == page) {
+			page_found = 1;
+			break;
+		}
+		trav = trav->next;
+	}
+  
+	if (!page_found) {
+		waiter = CALLOC (1, sizeof (ioc_waitq_t));
+		ERR_ABORT (waiter);
+		waiter->data = page;
+		waiter->next = ioc_inode->waitq;
+		ioc_inode->waitq = waiter;
+	}
+  
+	return 0;
+}
+
+/*
+ * ioc_cache_validate -
+ *
+ * @frame:
+ * @ioc_inode:
+ * @fd:
+ *
+ */
+static int32_t
+ioc_cache_validate (call_frame_t *frame,
+		    ioc_inode_t *ioc_inode,
+		    fd_t *fd,
+		    ioc_page_t *page)
+{
+	call_frame_t *validate_frame = NULL;
+	ioc_local_t *validate_local = NULL;
+
+	validate_local = CALLOC (1, sizeof (ioc_local_t));
+	ERR_ABORT (validate_local);
+	validate_frame = copy_frame (frame);
+	validate_local->fd = fd_ref (fd);
+	validate_local->inode = ioc_inode;
+	validate_frame->local = validate_local;
+    
+	STACK_WIND (validate_frame,
+		    ioc_cache_validate_cbk,
+		    FIRST_CHILD (frame->this),
+		    FIRST_CHILD (frame->this)->fops->fstat,
+		    fd);
+
+	return 0;
+}
+
+static inline uint32_t
+is_match (const char *path,
+	  const char *pattern)
+{
+	char *pathname = strdup (path);
+	int32_t ret = 0;
+
+	ret = fnmatch (pattern, path, FNM_NOESCAPE);
+  
+	free (pathname);
+  
+	return (ret == 0);
+}
+
+static uint32_t
+ioc_get_priority (ioc_table_t *table, 
+		  const char *path)
+{
+	uint32_t priority = 0;
+	struct ioc_priority *curr = NULL;
+  
+	list_for_each_entry (curr, &table->priority_list, list) {
+		if (is_match (path, curr->pattern)) 
+			priority = curr->priority;
+	}
+
+	return priority;
+}
+
+/* 
+ * ioc_open_cbk - open callback for io cache
+ *
+ * @frame: call frame
+ * @cookie:
+ * @this:
+ * @op_ret:
+ * @op_errno:
+ * @fd:
+ *
+ */
+int32_t
+ioc_open_cbk (call_frame_t *frame,
+	      void *cookie,
+	      xlator_t *this,
+	      int32_t op_ret,
+	      int32_t op_errno,
+	      fd_t *fd)
+{
+	uint64_t     tmp_ioc_inode = 0;
+	ioc_local_t *local = frame->local;
+	ioc_table_t *table = this->private;
+	ioc_inode_t *ioc_inode = NULL;
+	inode_t *inode = local->file_loc.inode;
+	uint32_t weight = 0;
+	const char *path = local->file_loc.path;
+
+	if (op_ret != -1) {
+		/* look for ioc_inode corresponding to this fd */
+		LOCK (&fd->inode->lock);
+		//{
+
+		inode_ctx_get (fd->inode, this, &tmp_ioc_inode);
+		ioc_inode = (ioc_inode_t *)(long)tmp_ioc_inode;
+      
+		if (!ioc_inode) {
+			/* this is the first time someone is opening this 
+			   file, assign weight 
+			*/
+			weight = ioc_get_priority (table, path);
+ 
+			ioc_inode = ioc_inode_update (table, inode, weight);
+			inode_ctx_put (fd->inode, this, 
+				       (uint64_t)(long)ioc_inode);
+		} else {
+			ioc_table_lock (ioc_inode->table);
+			//{
+			list_move_tail (&ioc_inode->inode_lru,
+					&table->inode_lru[ioc_inode->weight]);
+			//}
+			ioc_table_unlock (ioc_inode->table);
+		}
+
+		//}
+		UNLOCK (&fd->inode->lock);
+
+		/* If mandatory locking has been enabled on this file,
+		   we disable caching on it */
+		if (((inode->st_mode & S_ISGID) && 
+		     !(inode->st_mode & S_IXGRP))) {
+			fd_ctx_set (fd, this, 1);
+		}
+  
+		/* If O_DIRECT open, we disable caching on it */
+		if ((local->flags & O_DIRECT)){
+			/* O_DIRECT is only for one fd, not the inode 
+			 * as a whole 
+			 */
+			fd_ctx_set (fd, this, 1);
+		}
+	}
+
+	FREE (local);
+	frame->local = NULL;
+
+	STACK_UNWIND (frame, op_ret, op_errno, fd);
+
+	return 0;
+}
+
+/*
+ * ioc_create_cbk - create callback for io cache
+ *
+ * @frame: call frame
+ * @cookie:
+ * @this:
+ * @op_ret:
+ * @op_errno:
+ * @fd:
+ * @inode:
+ * @buf:
+ *
+ */
+int32_t
+ioc_create_cbk (call_frame_t *frame,
+		void *cookie,
+		xlator_t *this,
+		int32_t op_ret,
+		int32_t op_errno,
+		fd_t *fd,
+		inode_t *inode,
+		struct stat *buf)
+{
+	ioc_local_t *local = frame->local;
+	ioc_table_t *table = this->private;
+	ioc_inode_t *ioc_inode = NULL;
+	uint32_t weight = 0;
+	const char *path = local->file_loc.path;
+
+	if (op_ret != -1) {
+		{
+			/* assign weight */
+			weight = ioc_get_priority (table, path);
+
+			ioc_inode = ioc_inode_update (table, inode, weight);
+			LOCK (&fd->inode->lock);
+			{
+				inode_ctx_put (fd->inode, this, 
+					       (uint64_t)(long)ioc_inode);
+			}
+			UNLOCK (&fd->inode->lock);
+		}
+		/* If mandatory locking has been enabled on this file,
+		   we disable caching on it */
+		if ((inode->st_mode & S_ISGID) && 
+		    !(inode->st_mode & S_IXGRP)) {
+			fd_ctx_set (fd, this, 1);
+		}
+
+		/* If O_DIRECT open, we disable caching on it */
+		if (local->flags & O_DIRECT){
+			/* O_DIRECT is only for one fd, not the inode 
+			 * as a whole 
+			 */
+			fd_ctx_set (fd, this, 1);
+		}
+    
+	}
+  
+	frame->local = NULL;
+	FREE (local);
+
+	STACK_UNWIND (frame, op_ret, op_errno, fd, inode, buf);
+
+	return 0;
+}
+
+/*
+ * ioc_open - open fop for io cache
+ * @frame:
+ * @this:
+ * @loc:
+ * @flags:
+ *
+ */
+int32_t
+ioc_open (call_frame_t *frame,
+	  xlator_t *this,
+	  loc_t *loc,
+	  int32_t flags,
+	  fd_t *fd)
+{
+  
+	ioc_local_t *local = CALLOC (1, sizeof (ioc_local_t));
+	ERR_ABORT (local);
+
+	local->flags = flags;
+	local->file_loc.path = loc->path;
+	local->file_loc.inode = loc->inode;
+  
+	frame->local = local;
+  
+	STACK_WIND (frame,
+		    ioc_open_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->open,
+		    loc,
+		    flags,
+		    fd);
+
+	return 0;
+}
+
+/*
+ * ioc_create - create fop for io cache
+ * 
+ * @frame:
+ * @this:
+ * @pathname:
+ * @flags:
+ * @mode:
+ *
+ */
+int32_t
+ioc_create (call_frame_t *frame,
+	    xlator_t *this,
+	    loc_t *loc,
+	    int32_t flags,
+	    mode_t mode,
+	    fd_t *fd)
+{
+	ioc_local_t *local = CALLOC (1, sizeof (ioc_local_t));
+	ERR_ABORT (local);
+
+	local->flags = flags;
+	local->file_loc.path = loc->path;
+	frame->local = local;
+
+	STACK_WIND (frame, ioc_create_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->create,
+		    loc, flags, mode, fd);
+	return 0;
+}
+
+
+
+
+/*
+ * ioc_release - release fop for io cache
+ * 
+ * @frame:
+ * @this:
+ * @fd:
+ *
+ */
+int32_t
+ioc_release (xlator_t *this,
+	     fd_t *fd)
+{
+	return 0;
+}
+
+/* 
+ * ioc_readv_disabled_cbk 
+ * @frame:
+ * @cookie:
+ * @this:
+ * @op_ret:
+ * @op_errno:
+ * @vector:
+ * @count:
+ *
+ */ 
+int32_t
+ioc_readv_disabled_cbk (call_frame_t *frame, 
+			void *cookie,
+			xlator_t *this,
+			int32_t op_ret,
+			int32_t op_errno,
+			struct iovec *vector,
+			int32_t count,
+			struct stat *stbuf)
+{
+	STACK_UNWIND (frame, op_ret, op_errno, vector, count, stbuf);
+	return 0;
+}
+
+
+int32_t
+ioc_need_prune (ioc_table_t *table)
+{
+	int64_t cache_difference = 0;
+  
+	ioc_table_lock (table);
+	{
+		cache_difference = table->cache_used - table->cache_size;
+	}
+	ioc_table_unlock (table);
+
+	if (cache_difference > 0)
+		return 1;
+	else 
+		return 0;
+}
+
+/*
+ * dispatch_requests -
+ * 
+ * @frame:
+ * @inode:
+ *
+ * 
+ */
+static void
+dispatch_requests (call_frame_t *frame,
+		   ioc_inode_t *ioc_inode,
+		   fd_t *fd,
+		   off_t offset,
+		   size_t size)
+{
+	ioc_local_t *local = frame->local;
+	ioc_table_t *table = ioc_inode->table;
+	ioc_page_t  *trav = NULL;
+	ioc_waitq_t *waitq = NULL;
+	off_t   rounded_offset = 0;
+	off_t   rounded_end = 0;
+	off_t   trav_offset = 0;
+	int32_t fault = 0;
+	int8_t  need_validate = 0;
+	int8_t  might_need_validate = 0;  /* if a page exists, do we need 
+					    to validate it? */
+
+	rounded_offset = floor (offset, table->page_size);
+	rounded_end = roof (offset + size, table->page_size);
+	trav_offset = rounded_offset;
+
+	/* once a frame does read, it should be waiting on something */
+	local->wait_count++;
+
+	/* Requested region can fall in three different pages,
+	 * 1. Ready - region is already in cache, we just have to serve it.
+	 * 2. In-transit - page fault has been generated on this page, we need
+	 *    to wait till the page is ready
+	 * 3. Fault - page is not in cache, we have to generate a page fault
+	 */
+
+	might_need_validate = ioc_inode_need_revalidate (ioc_inode);
+
+	while (trav_offset < rounded_end) {
+		size_t trav_size = 0;
+		off_t local_offset = 0;
+
+		ioc_inode_lock (ioc_inode);
+		//{
+
+		/* look for requested region in the cache */
+		trav = ioc_page_get (ioc_inode, trav_offset);
+
+		local_offset = max (trav_offset, offset);
+		trav_size = min (((offset+size) - local_offset), 
+				 table->page_size);
+
+		if (!trav) {
+			/* page not in cache, we need to generate page fault */
+			trav = ioc_page_create (ioc_inode, trav_offset);
+			fault = 1;
+			if (!trav) {
+				gf_log (frame->this->name, GF_LOG_CRITICAL,
+					"ioc_page_create returned NULL");
+			}
+		} 
+
+		ioc_wait_on_page (trav, frame, local_offset, trav_size);
+
+		if (trav->ready) {
+			/* page found in cache */
+			if (!might_need_validate) {
+				/* fresh enough */
+				gf_log (frame->this->name, GF_LOG_DEBUG,
+					"cache hit for trav_offset=%"PRId64""
+					"/local_offset=%"PRId64"",
+					trav_offset, local_offset);
+				waitq = ioc_page_wakeup (trav);
+			} else {
+				/* if waitq already exists, fstat revalidate is
+				   already on the way */
+				if (!ioc_inode->waitq) {
+					need_validate = 1;
+				}
+				ioc_wait_on_inode (ioc_inode, trav);
+			}
+		}
+
+		//}
+		ioc_inode_unlock (ioc_inode);
+    
+		ioc_waitq_return (waitq);
+		waitq = NULL;
+
+		if (fault) {
+			fault = 0;
+			/* new page created, increase the table->cache_used */
+			ioc_page_fault (ioc_inode, frame, fd, trav_offset);
+		}
+
+		if (need_validate) {
+			need_validate = 0;
+			gf_log (frame->this->name, GF_LOG_DEBUG,
+				"sending validate request for "
+				"inode(%"PRId64") at offset=%"PRId64"",
+				fd->inode->ino, trav_offset);
+			ioc_cache_validate (frame, ioc_inode, fd, trav);
+		}
+    
+		trav_offset += table->page_size;
+	}
+
+	ioc_frame_return (frame);
+
+	if (ioc_need_prune (ioc_inode->table)) {
+		ioc_prune (ioc_inode->table);
+	}
+
+	return;
+}
+
+
+/*
+ * ioc_readv -
+ * 
+ * @frame:
+ * @this:
+ * @fd:
+ * @size:
+ * @offset:
+ *
+ */
+int32_t
+ioc_readv (call_frame_t *frame,
+	   xlator_t *this,
+	   fd_t *fd,
+	   size_t size,
+	   off_t offset)
+{
+	uint64_t     tmp_ioc_inode = 0;
+	ioc_inode_t *ioc_inode = NULL;
+	ioc_local_t *local = NULL;
+	uint32_t     weight = 0;
+
+	inode_ctx_get (fd->inode, this, &tmp_ioc_inode);
+	ioc_inode = (ioc_inode_t *)(long)tmp_ioc_inode;
+	if (!ioc_inode) {
+		/* caching disabled, go ahead with normal readv */
+		STACK_WIND (frame, 
+			    ioc_readv_disabled_cbk,
+			    FIRST_CHILD (frame->this), 
+			    FIRST_CHILD (frame->this)->fops->readv,
+			    fd, 
+			    size, 
+			    offset);
+		return 0;
+	}
+
+	if (!fd_ctx_get (fd, this, NULL)) {
+		/* disable caching for this fd, go ahead with normal readv */
+		STACK_WIND (frame, 
+			    ioc_readv_disabled_cbk,
+			    FIRST_CHILD (frame->this), 
+			    FIRST_CHILD (frame->this)->fops->readv,
+			    fd, 
+			    size, 
+			    offset);
+		return 0;
+	}
+
+	local = (ioc_local_t *) CALLOC (1, sizeof (ioc_local_t));
+	ERR_ABORT (local);
+	INIT_LIST_HEAD (&local->fill_list);
+
+	frame->local = local;  
+	local->pending_offset = offset;
+	local->pending_size = size;
+	local->offset = offset;
+	local->size = size;
+	local->inode = ioc_inode;
+
+	gf_log (this->name, GF_LOG_DEBUG,
+		"NEW REQ (%p) offset = %"PRId64" && size = %"GF_PRI_SIZET"", 
+		frame, offset, size);
+
+	weight = ioc_inode->weight;
+
+	ioc_table_lock (ioc_inode->table);
+	{
+		list_move_tail (&ioc_inode->inode_lru, 
+				&ioc_inode->table->inode_lru[weight]);
+	}
+	ioc_table_unlock (ioc_inode->table);
+
+	dispatch_requests (frame, ioc_inode, fd, offset, size);
+  
+	return 0;
+}
+
+/*
+ * ioc_writev_cbk -
+ * 
+ * @frame:
+ * @cookie:
+ * @this:
+ * @op_ret:
+ * @op_errno:
+ *
+ */
+int32_t
+ioc_writev_cbk (call_frame_t *frame,
+		void *cookie,
+		xlator_t *this,
+		int32_t op_ret,
+		int32_t op_errno,
+		struct stat *stbuf)
+{
+	ioc_local_t *local     = frame->local;
+	uint64_t     ioc_inode = 0;
+
+	inode_ctx_get (local->fd->inode, this, &ioc_inode);
+  
+	if (ioc_inode)
+		ioc_inode_flush ((ioc_inode_t *)(long)ioc_inode);
+
+	STACK_UNWIND (frame, op_ret, op_errno, stbuf);
+	return 0;
+}
+
+/*
+ * ioc_writev
+ * 
+ * @frame:
+ * @this:
+ * @fd:
+ * @vector:
+ * @count:
+ * @offset:
+ *
+ */
+int32_t
+ioc_writev (call_frame_t *frame,
+	    xlator_t *this,
+	    fd_t *fd,
+	    struct iovec *vector,
+	    int32_t count,
+	    off_t offset)
+{
+	ioc_local_t *local     = NULL;
+	uint64_t     ioc_inode = 0;
+	
+	local = CALLOC (1, sizeof (ioc_local_t));
+	ERR_ABORT (local);
+
+	/* TODO: why is it not fd_ref'ed */
+	local->fd = fd;
+	frame->local = local;
+
+	inode_ctx_get (fd->inode, this, &ioc_inode);
+	if (ioc_inode)
+		ioc_inode_flush ((ioc_inode_t *)(long)ioc_inode);
+
+	STACK_WIND (frame,
+		    ioc_writev_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->writev,
+		    fd,
+		    vector,
+		    count,
+		    offset);
+
+	return 0;
+}
+
+/*
+ * ioc_truncate_cbk -
+ * 
+ * @frame:
+ * @cookie:
+ * @this:
+ * @op_ret:
+ * @op_errno:
+ * @buf:
+ *
+ */
+int32_t 
+ioc_truncate_cbk (call_frame_t *frame,
+		  void *cookie,
+		  xlator_t *this,
+		  int32_t op_ret,
+		  int32_t op_errno,
+		  struct stat *buf)
+{
+
+	STACK_UNWIND (frame, op_ret, op_errno, buf);
+	return 0;
+}
+
+/*
+ * ioc_truncate -
+ * 
+ * @frame:
+ * @this:
+ * @loc:
+ * @offset:
+ *
+ */
+int32_t 
+ioc_truncate (call_frame_t *frame,
+	      xlator_t *this,
+	      loc_t *loc,
+	      off_t offset)
+{
+	uint64_t ioc_inode = 0;
+	inode_ctx_get (loc->inode, this, &ioc_inode);
+
+	if (ioc_inode)
+		ioc_inode_flush ((ioc_inode_t *)(long)ioc_inode);
+
+	STACK_WIND (frame,
+		    ioc_truncate_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->truncate,
+		    loc,
+		    offset);
+	return 0;
+}
+
+/*
+ * ioc_ftruncate -
+ * 
+ * @frame:
+ * @this:
+ * @fd:
+ * @offset:
+ *
+ */
+int32_t
+ioc_ftruncate (call_frame_t *frame,
+	       xlator_t *this,
+	       fd_t *fd,
+	       off_t offset)
+{
+	uint64_t ioc_inode = 0;
+	inode_ctx_get (fd->inode, this, &ioc_inode);
+
+	if (ioc_inode)
+		ioc_inode_flush ((ioc_inode_t *)(long)ioc_inode);
+
+	STACK_WIND (frame,
+		    ioc_truncate_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->ftruncate,
+		    fd,
+		    offset);
+	return 0;
+}
+
+int32_t
+ioc_lk_cbk (call_frame_t *frame,
+	    void *cookie,
+	    xlator_t *this,
+	    int32_t op_ret,
+	    int32_t op_errno,
+	    struct flock *lock)
+{
+	STACK_UNWIND (frame, op_ret, op_errno, lock);
+	return 0;
+}
+
+int32_t 
+ioc_lk (call_frame_t *frame,
+	xlator_t *this,
+	fd_t *fd,
+	int32_t cmd,
+	struct flock *lock)
+{
+	ioc_inode_t *ioc_inode = NULL;
+	uint64_t     tmp_inode = 0;
+
+	inode_ctx_get (fd->inode, this, &tmp_inode);
+	ioc_inode = (ioc_inode_t *)(long)tmp_inode;
+	if (!ioc_inode) {
+		gf_log (this->name, GF_LOG_ERROR,
+			"inode context is NULL: returning EBADFD");
+		STACK_UNWIND (frame, -1, EBADFD, NULL);
+		return 0;
+	}
+
+	ioc_inode_lock (ioc_inode);
+	{
+		gettimeofday (&ioc_inode->tv, NULL);
+	}
+	ioc_inode_unlock (ioc_inode);
+
+	STACK_WIND (frame, ioc_lk_cbk, 
+		    FIRST_CHILD (this),
+		    FIRST_CHILD (this)->fops->lk, fd, cmd, lock);
+	return 0;
+}
+
+int32_t
+ioc_get_priority_list (const char *opt_str, struct list_head *first)
+{
+	int32_t max_pri = 0;
+	char *tmp_str = NULL;
+	char *tmp_str1 = NULL;
+	char *tmp_str2 = NULL;
+	char *dup_str = NULL;
+	char *stripe_str = NULL;
+	char *pattern = NULL;
+	char *priority = NULL;
+	char *string = strdup (opt_str);
+	struct ioc_priority *curr = NULL;
+
+	/* Get the pattern for cache priority. 
+	 * "option priority *.jpg:1,abc*:2" etc 
+	 */
+	/* TODO: inode_lru in table is statically hard-coded to 5, 
+	 * should be changed to run-time configuration 
+	 */
+	stripe_str = strtok_r (string, ",", &tmp_str);
+	while (stripe_str) {
+		curr = CALLOC (1, sizeof (struct ioc_priority));
+		ERR_ABORT (curr);
+		list_add_tail (&curr->list, first);
+
+		dup_str = strdup (stripe_str);
+		pattern = strtok_r (dup_str, ":", &tmp_str1);
+		if (!pattern)
+			return -1;
+		priority = strtok_r (NULL, ":", &tmp_str1);
+		if (!priority)
+			return -1;
+		gf_log ("io-cache", 
+			GF_LOG_DEBUG, 
+			"ioc priority : pattern %s : priority %s", 
+			pattern,
+			priority);
+		curr->pattern = strdup (pattern);
+		curr->priority = strtol (priority, &tmp_str2, 0);
+		if (tmp_str2 && (*tmp_str2))
+			return -1;
+		else
+			max_pri = max (max_pri, curr->priority);
+		stripe_str = strtok_r (NULL, ",", &tmp_str);
+	}
+
+	return max_pri;
+}
+
+/*
+ * init - 
+ * @this:
+ *
+ */
+int32_t 
+init (xlator_t *this)
+{
+	ioc_table_t *table;
+	dict_t *options = this->options;
+	uint32_t index = 0;
+	char *page_size_string = NULL;
+	char *cache_size_string = NULL;
+
+	if (!this->children || this->children->next) {
+		gf_log (this->name, GF_LOG_ERROR,
+			"FATAL: io-cache not configured with exactly "
+			"one child");
+		return -1;
+	}
+
+	if (!this->parents) {
+		gf_log (this->name, GF_LOG_WARNING,
+			"dangling volume. check volfile ");
+	}
+
+	table = (void *) CALLOC (1, sizeof (*table));
+	ERR_ABORT (table);
+  
+	table->xl = this;
+	table->page_size = IOC_PAGE_SIZE;
+	table->cache_size = IOC_CACHE_SIZE;
+
+	if (dict_get (options, "page-size"))
+		page_size_string = data_to_str (dict_get (options, 
+							  "page-size"));
+
+	if (page_size_string) {
+		if (gf_string2bytesize (page_size_string, 
+					&table->page_size) != 0) {
+			gf_log ("io-cache", GF_LOG_ERROR, 
+				"invalid number format \"%s\" of "
+				"\"option page-size\"", 
+				page_size_string);
+			return -1;
+		}
+		gf_log (this->name, GF_LOG_DEBUG, 
+			"using page-size %"PRIu64"",  table->page_size);
+	}
+  
+	if (dict_get (options, "cache-size"))
+		cache_size_string = data_to_str (dict_get (options, 
+							   "cache-size"));
+	if (cache_size_string) {
+		if (gf_string2bytesize (cache_size_string, 
+					&table->cache_size) != 0) {
+			gf_log ("io-cache", GF_LOG_ERROR, 
+				"invalid number format \"%s\" of "
+				"\"option cache-size\"", 
+				cache_size_string);
+			return -1;
+		}
+      
+		gf_log (this->name, GF_LOG_DEBUG, 
+			"using cache-size %"PRIu64"", table->cache_size);
+	}
+  
+	table->cache_timeout = 1;
+
+	if (dict_get (options, "cache-timeout")) {
+		table->cache_timeout = 
+			data_to_uint32 (dict_get (options,
+						  "cache-timeout"));
+		gf_log (this->name, GF_LOG_DEBUG,
+			"Using %d seconds to revalidate cache",
+			table->cache_timeout);
+	}
+
+	INIT_LIST_HEAD (&table->priority_list);
+	if (dict_get (options, "priority")) {
+		char *option_list = data_to_str (dict_get (options, 
+							   "priority"));
+		gf_log (this->name, GF_LOG_DEBUG,
+			"option path %s", option_list);
+		/* parse the list of pattern:priority */
+		table->max_pri = ioc_get_priority_list (option_list, 
+							&table->priority_list);
+    
+		if (table->max_pri == -1)
+			return -1;
+	}
+	table->max_pri ++;
+	INIT_LIST_HEAD (&table->inodes);
+  
+	table->inode_lru = CALLOC (table->max_pri, sizeof (struct list_head));
+	ERR_ABORT (table->inode_lru);
+	for (index = 0; index < (table->max_pri); index++)
+		INIT_LIST_HEAD (&table->inode_lru[index]);
+
+	pthread_mutex_init (&table->table_lock, NULL);
+	this->private = table;
+	return 0;
+}
+
+/*
+ * fini -
+ * 
+ * @this:
+ *
+ */
+void
+fini (xlator_t *this)
+{
+	ioc_table_t *table = this->private;
+
+	pthread_mutex_destroy (&table->table_lock);
+	FREE (table);
+
+	this->private = NULL;
+	return;
+}
+
+struct xlator_fops fops = {
+	.open        = ioc_open,
+	.create      = ioc_create,
+	.readv       = ioc_readv,
+	.writev      = ioc_writev,
+	.truncate    = ioc_truncate,
+	.ftruncate   = ioc_ftruncate,
+	.utimens     = ioc_utimens,
+	.lookup      = ioc_lookup,
+	.lk          = ioc_lk
+};
+
+struct xlator_mops mops = {
+};
+
+struct xlator_cbks cbks = {
+	.forget      = ioc_forget,
+  	.release     = ioc_release
+};
+
+struct volume_options options[] = {
+	{ .key  = {"priority"}, 
+	  .type = GF_OPTION_TYPE_ANY 
+	},
+	{ .key  = {"cache-timeout", "force-revalidate-timeout"},
+	  .type = GF_OPTION_TYPE_INT,
+	  .min  = 0, 
+	  .max  = 60 
+	}, 
+	{ .key  = {"page-size"}, 
+	  .type = GF_OPTION_TYPE_SIZET, 
+	  .min  = 16 * GF_UNIT_KB, 
+	  .max  =  4 * GF_UNIT_MB 
+	},
+	{ .key  = {"cache-size"}, 
+	  .type = GF_OPTION_TYPE_SIZET,
+	  .min  = 4 * GF_UNIT_MB, 
+	  .max  = 6 * GF_UNIT_GB 
+	},
+	{ .key = {NULL} },
+};
diff --git a/xlators/performance/io-cache/src/io-cache.h b/xlators/performance/io-cache/src/io-cache.h
new file mode 100644
index 00000000000..e997f6e7ca6
--- /dev/null
+++ b/xlators/performance/io-cache/src/io-cache.h
@@ -0,0 +1,330 @@
+/*
+   Copyright (c) 2007, 2008 Z RESEARCH, Inc. <http://www.zresearch.com>
+   This file is part of GlusterFS.
+
+   GlusterFS is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published
+   by the Free Software Foundation; either version 3 of the License,
+   or (at your option) any later version.
+
+   GlusterFS is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see
+   <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __IO_CACHE_H
+#define __IO_CACHE_H
+
+#ifndef _CONFIG_H
+#define _CONFIG_H
+#include "config.h"
+#endif
+
+#include <sys/types.h>
+#include "compat-errno.h"
+
+#include "glusterfs.h"
+#include "logging.h"
+#include "dict.h"
+#include "xlator.h"
+#include "common-utils.h"
+#include "call-stub.h"
+#include <sys/time.h>
+#include <fnmatch.h>
+
+#define IOC_PAGE_SIZE    (1024 * 128)   /* 128KB */
+#define IOC_CACHE_SIZE   (32 * 1024 * 1024)
+
+struct ioc_table;
+struct ioc_local;
+struct ioc_page;
+struct ioc_inode;
+
+struct ioc_priority {
+	struct list_head list;
+	char *pattern;
+	uint32_t priority;
+};
+
+/*
+ * ioc_waitq - this structure is used to represents the waiting 
+ *             frames on a page
+ *
+ * @next: pointer to next object in waitq
+ * @data: pointer to the frame which is waiting
+ */
+struct ioc_waitq {
+	struct ioc_waitq *next;
+	void *data;
+	off_t pending_offset;
+	size_t pending_size;
+};
+
+/*
+ * ioc_fill - 
+ *
+ */
+struct ioc_fill {
+	struct list_head list;  /* list of ioc_fill structures of a frame */
+	off_t offset;          
+	size_t size;           
+	struct iovec *vector;  
+	int32_t count;
+	dict_t *refs;
+};
+
+struct ioc_local {
+	mode_t mode;
+	int32_t flags;
+	loc_t file_loc;
+	off_t offset;
+	size_t size;
+	int32_t op_ret;
+	int32_t op_errno;
+	struct list_head fill_list;      /* list of ioc_fill structures */
+	off_t pending_offset;            /* offset from this frame should continue */
+	size_t pending_size;             /* size of data this frame is waiting on */
+	struct ioc_inode *inode;
+	int32_t wait_count;
+	pthread_mutex_t local_lock;
+	struct ioc_waitq *waitq;
+	void *stub;
+	fd_t *fd;
+	int32_t need_xattr;
+	dict_t *xattr_req;
+};
+
+/*
+ * ioc_page - structure to store page of data from file 
+ *
+ */
+struct ioc_page {
+	struct list_head pages;
+	struct list_head page_lru;
+	struct ioc_inode *inode;   /* inode this page belongs to */
+	struct ioc_priority *priority;
+	char dirty;
+	char ready;
+	struct iovec *vector;
+	int32_t count;
+	off_t offset;
+	size_t size;
+	struct ioc_waitq *waitq;
+	dict_t *ref;
+	pthread_mutex_t page_lock;
+};
+
+struct ioc_inode {
+	struct ioc_table *table;
+	struct list_head pages;      /* list of pages of this inode */
+	struct list_head inode_list; /* list of inodes, maintained by io-cache translator */
+	struct list_head inode_lru;
+	struct list_head page_lru;
+	struct ioc_waitq *waitq;
+	pthread_mutex_t inode_lock;
+	uint32_t weight;             /* weight of the inode, increases on each read */
+	time_t mtime;             /* mtime of the server file when last cached */
+	struct timeval tv;           /* time-stamp at last re-validate */
+};
+
+struct ioc_table {
+	uint64_t page_size;
+	uint64_t cache_size;
+	uint64_t cache_used;
+	struct list_head inodes; /* list of inodes cached */
+	struct list_head active; 
+	struct list_head *inode_lru;
+	struct list_head priority_list;
+	int32_t readv_count;
+	pthread_mutex_t table_lock;
+	xlator_t *xl;
+	uint32_t inode_count;
+	int32_t cache_timeout;
+	int32_t max_pri;
+};
+
+typedef struct ioc_table ioc_table_t;
+typedef struct ioc_local ioc_local_t;
+typedef struct ioc_page ioc_page_t;
+typedef struct ioc_inode ioc_inode_t;
+typedef struct ioc_waitq ioc_waitq_t;
+typedef struct ioc_fill ioc_fill_t;
+
+void *
+str_to_ptr (char *string);
+
+char *
+ptr_to_str (void *ptr);
+
+int32_t 
+ioc_readv_disabled_cbk (call_frame_t *frame,
+			void *cookie,
+			xlator_t *this,
+			int32_t op_ret,
+			int32_t op_errno,
+			struct iovec *vector,
+			int32_t count,
+			struct stat *stbuf);
+
+ioc_page_t *
+ioc_page_get (ioc_inode_t *ioc_inode,
+	      off_t offset);
+
+ioc_page_t *
+ioc_page_create (ioc_inode_t *ioc_inode,
+		 off_t offset);
+
+void
+ioc_page_fault (ioc_inode_t *ioc_inode,
+		call_frame_t *frame,
+		fd_t *fd,
+		off_t offset);
+void
+ioc_wait_on_page (ioc_page_t *page,
+		  call_frame_t *frame,
+		  off_t offset,
+		  size_t size);
+
+ioc_waitq_t *
+ioc_page_wakeup (ioc_page_t *page);
+
+void
+ioc_page_flush (ioc_page_t *page);
+
+ioc_waitq_t *
+ioc_page_error (ioc_page_t *page,
+		int32_t op_ret,
+		int32_t op_errno);
+void
+ioc_page_purge (ioc_page_t *page);
+
+void
+ioc_frame_return (call_frame_t *frame);
+
+void
+ioc_waitq_return (ioc_waitq_t *waitq);
+
+void
+ioc_frame_fill (ioc_page_t *page,
+		call_frame_t *frame,
+		off_t offset,
+		size_t size);
+
+#define ioc_inode_lock(ioc_inode)					\
+	do {								\
+		gf_log (ioc_inode->table->xl->name, GF_LOG_DEBUG,	\
+			"locked inode(%p)", ioc_inode);			\
+		pthread_mutex_lock (&ioc_inode->inode_lock);		\
+	} while (0)
+
+
+#define ioc_inode_unlock(ioc_inode)					\
+	do {								\
+		gf_log (ioc_inode->table->xl->name, GF_LOG_DEBUG,	\
+			"unlocked inode(%p)", ioc_inode);		\
+		pthread_mutex_unlock (&ioc_inode->inode_lock);		\
+	} while (0)
+
+
+#define ioc_table_lock(table)					\
+	do {							\
+		gf_log (table->xl->name, GF_LOG_DEBUG,		\
+			"locked table(%p)", table);		\
+		pthread_mutex_lock (&table->table_lock);	\
+	} while (0)
+
+
+#define ioc_table_unlock(table)					\
+	do {							\
+		gf_log (table->xl->name, GF_LOG_DEBUG,		\
+			"unlocked table(%p)", table);		\
+		pthread_mutex_unlock (&table->table_lock);	\
+	} while (0)
+
+
+#define ioc_local_lock(local)						\
+	do {								\
+		gf_log (local->inode->table->xl->name, GF_LOG_DEBUG,	\
+			"locked local(%p)", local);			\
+		pthread_mutex_lock (&local->local_lock);		\
+	} while (0)
+
+
+#define ioc_local_unlock(local)						\
+	do {								\
+		gf_log (local->inode->table->xl->name, GF_LOG_DEBUG,	\
+			"unlocked local(%p)", local);			\
+		pthread_mutex_unlock (&local->local_lock);		\
+	} while (0)
+
+
+#define ioc_page_lock(page)						\
+	do {								\
+		gf_log (page->inode->table->xl->name, GF_LOG_DEBUG,	\
+			"locked page(%p)", page);			\
+		pthread_mutex_lock (&page->page_lock);			\
+	} while (0)
+
+
+#define ioc_page_unlock(page)						\
+	do {								\
+		gf_log (page->inode->table->xl->name, GF_LOG_DEBUG,	\
+			"unlocked page(%p)", page);			\
+		pthread_mutex_unlock (&page->page_lock);		\
+	} while (0)
+
+
+static inline uint64_t
+time_elapsed (struct timeval *now,
+	      struct timeval *then)
+{
+	uint64_t sec = now->tv_sec - then->tv_sec;
+
+	if (sec)
+		return sec;
+  
+	return 0;
+}
+
+ioc_inode_t *
+ioc_inode_search (ioc_table_t *table,
+		  inode_t *inode);
+
+void 
+ioc_inode_destroy (ioc_inode_t *ioc_inode);
+
+ioc_inode_t *
+ioc_inode_update (ioc_table_t *table,
+		  inode_t *inode,
+		  uint32_t weight);
+
+int64_t 
+ioc_page_destroy (ioc_page_t *page);
+
+int32_t
+__ioc_inode_flush (ioc_inode_t *ioc_inode);
+
+void
+ioc_inode_flush (ioc_inode_t *ioc_inode);
+
+void
+ioc_inode_wakeup (call_frame_t *frame, 
+		  ioc_inode_t *ioc_inode, 
+		  struct stat *stbuf);
+
+int8_t
+ioc_cache_still_valid (ioc_inode_t *ioc_inode,
+		       struct stat *stbuf);
+
+int32_t
+ioc_prune (ioc_table_t *table);
+
+int32_t
+ioc_need_prune (ioc_table_t *table);
+
+#endif /* __READ_AHEAD_H */
diff --git a/xlators/performance/io-cache/src/ioc-inode.c b/xlators/performance/io-cache/src/ioc-inode.c
new file mode 100644
index 00000000000..2e2e561dd23
--- /dev/null
+++ b/xlators/performance/io-cache/src/ioc-inode.c
@@ -0,0 +1,201 @@
+/*
+  Copyright (c) 2007, 2008, 2009 Z RESEARCH, Inc. <http://www.zresearch.com>
+  This file is part of GlusterFS.
+
+  GlusterFS is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published
+  by the Free Software Foundation; either version 3 of the License,
+  or (at your option) any later version.
+
+  GlusterFS is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see
+  <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef _CONFIG_H
+#define _CONFIG_H
+#include "config.h"
+#endif
+
+#include "io-cache.h"
+
+
+/*
+ * str_to_ptr - convert a string to pointer
+ * @string: string
+ *
+ */
+void *
+str_to_ptr (char *string)
+{
+	void *ptr = (void *)strtoul (string, NULL, 16);
+	return ptr;
+}
+
+
+/*
+ * ptr_to_str - convert a pointer to string
+ * @ptr: pointer
+ *
+ */
+char *
+ptr_to_str (void *ptr)
+{
+	char *str;
+	asprintf (&str, "%p", ptr);
+	return str;
+}
+
+void
+ioc_inode_wakeup (call_frame_t *frame,
+		  ioc_inode_t *ioc_inode, 
+		  struct stat *stbuf)
+{
+	ioc_waitq_t *waiter = NULL, *waited = NULL;
+	ioc_waitq_t *page_waitq = NULL;
+	int8_t cache_still_valid = 1;
+	ioc_local_t *local = frame->local;
+	int8_t need_fault = 0;
+	ioc_page_t *waiter_page = NULL;
+
+	ioc_inode_lock (ioc_inode);
+	{
+		waiter = ioc_inode->waitq;
+		ioc_inode->waitq = NULL;
+	}
+	ioc_inode_unlock (ioc_inode);
+
+	if (stbuf)
+		cache_still_valid = ioc_cache_still_valid (ioc_inode, stbuf);
+	else
+		cache_still_valid = 0;
+
+	if (!waiter) {
+		gf_log (frame->this->name, GF_LOG_DEBUG,
+			"cache validate called without any "
+			"page waiting to be validated");
+	}
+
+	while (waiter) {
+		waiter_page = waiter->data;
+		page_waitq = NULL;
+    
+		if (waiter_page) {
+			if (cache_still_valid) {
+				/* cache valid, wake up page */
+				ioc_inode_lock (ioc_inode);
+				{
+					page_waitq = 
+						ioc_page_wakeup (waiter_page);
+				}
+				ioc_inode_unlock (ioc_inode);
+				if (page_waitq)
+					ioc_waitq_return (page_waitq);
+			} else {
+				/* cache invalid, generate page fault and set 
+				 * page->ready = 0, to avoid double faults  
+				 */
+				ioc_inode_lock (ioc_inode);
+	
+				if (waiter_page->ready) {
+					waiter_page->ready = 0;
+					need_fault = 1;
+				} else {
+					gf_log (frame->this->name, 
+						GF_LOG_DEBUG,
+						"validate frame(%p) is waiting"
+						"for in-transit page = %p",
+						frame, waiter_page);
+				}
+	
+				ioc_inode_unlock (ioc_inode);
+      
+				if (need_fault) {
+					need_fault = 0;
+					ioc_page_fault (ioc_inode, frame, 
+							local->fd, 
+							waiter_page->offset);
+				}
+			}
+		}
+
+		waited = waiter;
+		waiter = waiter->next;
+    
+		waited->data = NULL;
+		free (waited);
+	}
+}
+
+/* 
+ * ioc_inode_update - create a new ioc_inode_t structure and add it to 
+ *                    the table table. fill in the fields which are derived 
+ *                    from inode_t corresponding to the file
+ * 
+ * @table: io-table structure
+ * @inode: inode structure
+ *
+ * not for external reference
+ */
+ioc_inode_t *
+ioc_inode_update (ioc_table_t *table, 
+		  inode_t *inode,
+		  uint32_t weight)
+{
+	ioc_inode_t *ioc_inode = CALLOC (1, sizeof (ioc_inode_t));
+	ERR_ABORT (ioc_inode);
+  
+	ioc_inode->table = table;
+ 
+	/* initialize the list for pages */
+	INIT_LIST_HEAD (&ioc_inode->pages);
+	INIT_LIST_HEAD (&ioc_inode->page_lru);
+
+	ioc_table_lock (table);
+
+	table->inode_count++;
+	list_add (&ioc_inode->inode_list, &table->inodes);
+	list_add_tail (&ioc_inode->inode_lru, &table->inode_lru[weight]);
+
+	gf_log (table->xl->name,
+		GF_LOG_DEBUG,
+		"adding to inode_lru[%d]", weight);
+
+	ioc_table_unlock (table);
+
+	pthread_mutex_init (&ioc_inode->inode_lock, NULL);
+	ioc_inode->weight = weight;
+  
+	return ioc_inode;
+}
+
+
+/* 
+ * ioc_inode_destroy - destroy an ioc_inode_t object.
+ *
+ * @inode: inode to destroy
+ *
+ * to be called only from ioc_forget. 
+ */
+void
+ioc_inode_destroy (ioc_inode_t *ioc_inode)
+{
+	ioc_table_t *table = ioc_inode->table;
+
+	ioc_table_lock (table);
+	table->inode_count--;
+	list_del (&ioc_inode->inode_list);
+	list_del (&ioc_inode->inode_lru);
+	ioc_table_unlock (table);
+  
+	ioc_inode_flush (ioc_inode);
+
+	pthread_mutex_destroy (&ioc_inode->inode_lock);
+	free (ioc_inode);
+}
+
diff --git a/xlators/performance/io-cache/src/page.c b/xlators/performance/io-cache/src/page.c
new file mode 100644
index 00000000000..e549f0bb547
--- /dev/null
+++ b/xlators/performance/io-cache/src/page.c
@@ -0,0 +1,778 @@
+/*
+   Copyright (c) 2007, 2008, 2009 Z RESEARCH, Inc. <http://www.zresearch.com>
+   This file is part of GlusterFS.
+
+   GlusterFS is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published
+   by the Free Software Foundation; either version 3 of the License,
+   or (at your option) any later version.
+
+   GlusterFS is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see
+   <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef _CONFIG_H
+#define _CONFIG_H
+#include "config.h"
+#endif
+
+#include "glusterfs.h"
+#include "logging.h"
+#include "dict.h"
+#include "xlator.h"
+#include "io-cache.h"
+#include <assert.h>
+#include <sys/time.h>
+
+ioc_page_t *
+ioc_page_get (ioc_inode_t *ioc_inode,
+	      off_t offset)
+{
+	int8_t       found = 0;
+	ioc_page_t  *page = NULL;
+	ioc_table_t *table = ioc_inode->table;
+	off_t        rounded_offset = floor (offset, table->page_size);
+
+	if (list_empty (&ioc_inode->pages)) {
+		return NULL;
+	}
+
+	list_for_each_entry (page, &ioc_inode->pages, pages) {
+		if (page->offset == rounded_offset) {
+			found = 1;
+			break;
+		}
+	}
+
+	/* was previously returning ioc_inode itself.., 
+	 * 1st of its type and found one more downstairs :O */
+	if (!found){
+		page = NULL;
+	} else {
+		/* push the page to the end of the lru list */
+		list_move_tail (&page->page_lru, &ioc_inode->page_lru);
+	}
+
+	return page;
+}
+
+
+/*
+ * ioc_page_destroy -
+ *
+ * @page:
+ *
+ */
+int64_t
+ioc_page_destroy (ioc_page_t *page)
+{
+	int64_t page_size = 0;
+
+	page_size = page->size;
+
+	if (page->waitq) {
+		/* frames waiting on this page, do not destroy this page */
+		page_size = -1;
+	} else {
+
+		list_del (&page->pages);
+		list_del (&page->page_lru);
+    
+		gf_log (page->inode->table->xl->name, GF_LOG_DEBUG,
+			"destroying page = %p, offset = %"PRId64" "
+			"&& inode = %p",
+			page, page->offset, page->inode);
+    
+		if (page->vector){
+			dict_unref (page->ref);
+			free (page->vector);
+			page->vector = NULL;
+		}
+    
+		page->inode = NULL;
+    
+	}
+
+	if (page_size != -1) {
+		pthread_mutex_destroy (&page->page_lock);
+		free (page);
+	}
+
+	return page_size;
+}
+
+/*
+ * ioc_prune - prune the cache. we have a limit to the number of pages we
+ *             can have in-memory.
+ *
+ * @table: ioc_table_t of this translator
+ *
+ */
+int32_t
+ioc_prune (ioc_table_t *table)
+{
+	ioc_inode_t *curr = NULL, *next_ioc_inode = NULL;
+	ioc_page_t *page = NULL, *next = NULL;
+	int32_t ret = -1;
+	int32_t index = 0;
+	uint64_t size_to_prune = 0;
+	uint64_t size_pruned = 0;
+
+	ioc_table_lock (table);
+	{
+		size_to_prune = table->cache_used - table->cache_size;
+		/* take out the least recently used inode */
+		for (index=0; index < table->max_pri; index++) {
+			list_for_each_entry_safe (curr, next_ioc_inode, 
+						  &table->inode_lru[index], 
+						  inode_lru) {
+				/* prune page-by-page for this inode, till 
+				 * we reach the equilibrium */
+				ioc_inode_lock (curr);
+				/* { */
+
+				list_for_each_entry_safe (page, next, 
+							  &curr->page_lru, 
+							  page_lru) {
+					/* done with all pages, and not 
+					 * reached equilibrium yet??
+					 * continue with next inode in 
+					 * lru_list */
+					size_pruned += page->size;
+					ret = ioc_page_destroy (page);
+
+					if (ret != -1)
+						table->cache_used -= ret;
+	    
+					gf_log (table->xl->name,
+						GF_LOG_DEBUG,
+						"index = %d && table->cache_"
+						"used = %"PRIu64" && table->"
+						"cache_size = %"PRIu64, 
+						index, table->cache_used, 
+						table->cache_size);
+	    
+					if (size_pruned >= size_to_prune)
+						break;
+				} /* list_for_each_entry_safe(page...) */
+				if (list_empty (&curr->pages)) {
+					list_del_init (&curr->inode_lru);
+				}
+
+				/* } */ 
+				ioc_inode_unlock (curr);
+	
+				if (size_pruned >= size_to_prune)
+					break;
+			} /* list_for_each_entry_safe (curr...) */
+      
+			if (size_pruned >= size_to_prune)
+				break;
+		} /* for(index=0;...) */
+
+	} /* ioc_inode_table locked region end */
+	ioc_table_unlock (table);
+
+	return 0;
+}
+
+/*
+ * ioc_page_create - create a new page. 
+ *
+ * @ioc_inode: 
+ * @offset:
+ *
+ */
+ioc_page_t *
+ioc_page_create (ioc_inode_t *ioc_inode,
+		 off_t offset)
+{
+	ioc_table_t *table = ioc_inode->table;
+	ioc_page_t *page = NULL;
+	off_t rounded_offset = floor (offset, table->page_size);
+	ioc_page_t *newpage = CALLOC (1, sizeof (*newpage));
+	ERR_ABORT (newpage);
+  
+	if (ioc_inode)
+		table = ioc_inode->table;
+	else {
+		return NULL;
+	}
+   
+	newpage->offset = rounded_offset;
+	newpage->inode = ioc_inode;
+	pthread_mutex_init (&newpage->page_lock, NULL);
+
+	list_add_tail (&newpage->page_lru, &ioc_inode->page_lru);
+	list_add_tail (&newpage->pages, &ioc_inode->pages);
+
+	page = newpage;
+
+	gf_log ("io-cache", GF_LOG_DEBUG,
+		"returning new page %p", page);
+	return page;
+}
+
+/* 
+ * ioc_wait_on_page - pause a frame to wait till the arrival of a page. 
+ * here we need to handle the case when the frame who calls wait_on_page 
+ * himself has caused page_fault 
+ *
+ * @page: page to wait on
+ * @frame: call frame who is waiting on page
+ *
+ */
+void
+ioc_wait_on_page (ioc_page_t *page,
+		  call_frame_t *frame,
+		  off_t offset,
+		  size_t size)
+{
+	ioc_waitq_t *waitq = NULL;
+	ioc_local_t *local = frame->local;
+
+	waitq = CALLOC (1, sizeof (*waitq));
+	ERR_ABORT (waitq);
+  
+	gf_log (frame->this->name, GF_LOG_DEBUG,
+		"frame(%p) waiting on page = %p, offset=%"PRId64", "
+		"size=%"GF_PRI_SIZET"",
+		frame, page, offset, size);
+
+	waitq->data = frame;
+	waitq->next = page->waitq;
+	waitq->pending_offset = offset;
+	waitq->pending_size = size;
+	page->waitq = waitq;
+	/* one frame can wait only once on a given page, 
+	 * local->wait_count is number of pages a frame is waiting on */
+	ioc_local_lock (local);
+	{
+		local->wait_count++;
+	}
+	ioc_local_unlock (local);
+}
+
+
+/*
+ * ioc_cache_still_valid - see if cached pages ioc_inode are still valid 
+ * against given stbuf
+ *
+ * @ioc_inode:
+ * @stbuf:
+ *
+ * assumes ioc_inode is locked
+ */
+int8_t
+ioc_cache_still_valid (ioc_inode_t *ioc_inode,
+		       struct stat *stbuf)
+{
+	int8_t cache_still_valid = 1;
+  
+#if 0
+	if (!stbuf || (stbuf->st_mtime != ioc_inode->mtime) || 
+	    (stbuf->st_mtim.tv_nsec != ioc_inode->stbuf.st_mtim.tv_nsec))
+		cache_still_valid = 0;
+
+#else
+	if (!stbuf || (stbuf->st_mtime != ioc_inode->mtime))
+		cache_still_valid = 0;
+
+#endif
+
+#if 0
+	/* talk with avati@zresearch.com to enable this section */
+	if (!ioc_inode->mtime && stbuf) {
+		cache_still_valid = 1;
+		ioc_inode->mtime = stbuf->st_mtime;
+	}
+#endif
+
+	return cache_still_valid;
+}
+
+
+void
+ioc_waitq_return (ioc_waitq_t *waitq)
+{
+	ioc_waitq_t  *trav   = NULL;
+	ioc_waitq_t  *next   = NULL;
+	call_frame_t *frame = NULL;
+
+	for (trav = waitq; trav; trav = next) {
+		next = trav->next;
+
+		frame = trav->data;
+		ioc_frame_return (frame);
+		free (trav);
+	}
+}
+
+
+int
+ioc_fault_cbk (call_frame_t *frame,
+	       void *cookie,
+	       xlator_t *this,
+	       int32_t op_ret,
+	       int32_t op_errno,
+	       struct iovec *vector,
+	       int32_t count,
+	       struct stat *stbuf)
+{
+	ioc_local_t *local = frame->local;
+	off_t offset = local->pending_offset;
+	ioc_inode_t *ioc_inode = local->inode;
+	ioc_table_t *table = ioc_inode->table;
+	ioc_page_t *page = NULL;
+	off_t trav_offset = 0;
+	size_t payload_size = 0;
+	int32_t destroy_size = 0;
+	size_t page_size = 0;
+	ioc_waitq_t *waitq = NULL;
+
+	trav_offset = offset;  
+	payload_size = op_ret;
+
+	ioc_inode_lock (ioc_inode);
+	{
+		if (op_ret == -1 || 
+		    (op_ret >= 0 && 
+		     !ioc_cache_still_valid(ioc_inode, stbuf))) {
+			gf_log (ioc_inode->table->xl->name, GF_LOG_DEBUG,
+				"cache for inode(%p) is invalid. flushing "
+				"all pages", ioc_inode);
+			destroy_size = __ioc_inode_flush (ioc_inode);
+		} 
+    
+		if (op_ret >= 0)
+			ioc_inode->mtime = stbuf->st_mtime;
+    
+		gettimeofday (&ioc_inode->tv, NULL);
+    
+		if (op_ret < 0) {
+			/* error, readv returned -1 */
+			page = ioc_page_get (ioc_inode, offset);
+			if (page)
+				waitq = ioc_page_error (page, op_ret, 
+							op_errno);
+		} else {
+			gf_log (ioc_inode->table->xl->name, GF_LOG_DEBUG,
+				"op_ret = %d", op_ret);
+			page = ioc_page_get (ioc_inode, offset);
+			if (!page) {
+				/* page was flushed */
+				/* some serious bug ? */
+				gf_log (this->name, GF_LOG_DEBUG,
+					"wasted copy: %"PRId64"[+%"PRId64"] "
+					"ioc_inode=%p", offset, 
+					table->page_size, ioc_inode);
+			} else {
+				if (page->vector) {
+					dict_unref (page->ref);
+					free (page->vector);
+					page->vector = NULL;
+				}
+	
+				/* keep a copy of the page for our cache */
+				page->vector = iov_dup (vector, count);
+				page->count = count;
+				if (frame->root->rsp_refs) {
+					dict_ref (frame->root->rsp_refs);
+					page->ref = frame->root->rsp_refs;
+				} else {
+					/* TODO: we have got a response to 
+					 * our request and no data */
+					gf_log (this->name, GF_LOG_CRITICAL,
+						"frame>root>rsp_refs is null");
+				} /* if(frame->root->rsp_refs) */
+	
+				/* page->size should indicate exactly how 
+				 * much the readv call to the child
+				 * translator returned. earlier op_ret 
+				 * from child translator was used, which 
+				 * gave rise to a bug where reads from 
+				 * io-cached volume were resulting in 0 
+				 * byte replies */
+				page_size = iov_length(vector, count);
+	
+				page->size = page_size;
+
+				if (page->waitq) {
+					/* wake up all the frames waiting on 
+					 * this page, including 
+					 * the frame which triggered fault */
+					waitq = ioc_page_wakeup (page);
+				} /* if(page->waitq) */
+			} /* if(!page)...else */
+		} /* if(op_ret < 0)...else */
+	} /* ioc_inode locked region end */
+	ioc_inode_unlock (ioc_inode);
+
+	ioc_waitq_return (waitq);
+
+	if (page_size) {
+		ioc_table_lock (table);
+		{
+			table->cache_used += page_size;
+		}
+		ioc_table_unlock (table);
+	}
+
+	if (destroy_size) {
+		ioc_table_lock (table);
+		{
+			table->cache_used -= destroy_size;
+		}
+		ioc_table_unlock (table);
+	}
+
+	if (ioc_need_prune (ioc_inode->table)) {
+		ioc_prune (ioc_inode->table);
+	}
+
+	gf_log (this->name, GF_LOG_DEBUG, "fault frame %p returned", frame);
+	pthread_mutex_destroy (&local->local_lock);
+
+	fd_unref (local->fd);
+
+	STACK_DESTROY (frame->root);
+	return 0;
+}
+
+/*
+ * ioc_page_fault -
+ * 
+ * @ioc_inode:
+ * @frame:
+ * @fd:
+ * @offset:
+ *
+ */
+void
+ioc_page_fault (ioc_inode_t *ioc_inode,
+		call_frame_t *frame,
+		fd_t *fd,
+		off_t offset)
+{
+	ioc_table_t *table = ioc_inode->table;
+	call_frame_t *fault_frame = copy_frame (frame);
+	ioc_local_t *fault_local = CALLOC (1, sizeof (ioc_local_t));
+	ERR_ABORT (fault_local);
+
+	/* NOTE: copy_frame() means, the frame the fop whose fd_ref we 
+	 * are using till now won't be valid till we get reply from server. 
+	 * we unref this fd, in fault_cbk */
+	fault_local->fd = fd_ref (fd);
+
+	fault_frame->local = fault_local;
+	pthread_mutex_init (&fault_local->local_lock, NULL);
+
+	INIT_LIST_HEAD (&fault_local->fill_list);
+	fault_local->pending_offset = offset;
+	fault_local->pending_size = table->page_size;
+	fault_local->inode = ioc_inode;
+
+	gf_log (frame->this->name, GF_LOG_DEBUG,
+		"stack winding page fault for offset = %"PRId64" with "
+		"frame %p", offset, fault_frame);
+  
+	STACK_WIND (fault_frame, ioc_fault_cbk,
+		    FIRST_CHILD(fault_frame->this),
+		    FIRST_CHILD(fault_frame->this)->fops->readv,
+		    fd, table->page_size, offset);
+	return;
+}
+
+void
+ioc_frame_fill (ioc_page_t *page,
+		call_frame_t *frame,
+		off_t offset,
+		size_t size)
+{
+	ioc_local_t *local = frame->local;
+	ioc_fill_t *fill = NULL;
+	off_t src_offset = 0;
+	off_t dst_offset = 0;
+	ssize_t copy_size = 0;
+	ioc_inode_t *ioc_inode = page->inode;
+  
+	gf_log (frame->this->name, GF_LOG_DEBUG,
+		"frame (%p) offset = %"PRId64" && size = %"GF_PRI_SIZET" "
+		"&& page->size = %"GF_PRI_SIZET" && wait_count = %d", 
+		frame, offset, size, page->size, local->wait_count);
+
+	/* immediately move this page to the end of the page_lru list */
+	list_move_tail (&page->page_lru, &ioc_inode->page_lru);
+	/* fill local->pending_size bytes from local->pending_offset */
+	if (local->op_ret != -1 && page->size) {
+		if (offset > page->offset)
+			/* offset is offset in file, convert it to offset in 
+			 * page */
+			src_offset = offset - page->offset;
+		/*FIXME: since offset is the offset within page is the 
+		 * else case valid? */
+		else
+			/* local->pending_offset is in previous page. do not
+			 * fill until we have filled all previous pages */
+			dst_offset = page->offset - offset;
+
+		/* we have to copy from offset to either end of this page 
+		 * or till the requested size */
+		copy_size = min (page->size - src_offset,
+				 size - dst_offset);
+
+		if (copy_size < 0) {
+			/* if page contains fewer bytes and the required offset
+			   is beyond the page size in the page */
+			copy_size = src_offset = 0;
+		}
+    
+		gf_log (page->inode->table->xl->name, GF_LOG_DEBUG,
+			"copy_size = %"GF_PRI_SIZET" && src_offset = "
+			"%"PRId64" && dst_offset = %"PRId64"",
+			copy_size, src_offset, dst_offset);
+
+		{
+			ioc_fill_t *new = CALLOC (1, sizeof (*new));
+			ERR_ABORT (new);
+			new->offset = page->offset;
+			new->size = copy_size;
+			new->refs = dict_ref (page->ref);
+			new->count = iov_subset (page->vector,
+						 page->count,
+						 src_offset,
+						 src_offset + copy_size,
+						 NULL);
+			new->vector = CALLOC (new->count, 
+					      sizeof (struct iovec));
+			ERR_ABORT (new->vector);
+			new->count = iov_subset (page->vector,
+						 page->count,
+						 src_offset,
+						 src_offset + copy_size,
+						 new->vector);
+
+
+
+			/* add the ioc_fill to fill_list for this frame */
+			if (list_empty (&local->fill_list)) {
+				/* if list is empty, then this is the first 
+				 * time we are filling frame, add the 
+				 * ioc_fill_t to the end of list */
+				list_add_tail (&new->list, &local->fill_list);
+			} else {
+				int8_t found = 0;
+				/* list is not empty, we need to look for 
+				 * where this offset fits in list */
+				list_for_each_entry (fill, &local->fill_list, 
+						     list) {
+					if (fill->offset > new->offset) {
+						found = 1;
+						break;
+					}
+				}
+
+				if (found) {
+					found = 0;
+					list_add_tail (&new->list, 
+						       &fill->list);
+				} else {
+					list_add_tail (&new->list, 
+						       &local->fill_list);
+				}
+			}
+		}
+		local->op_ret += copy_size;
+	}
+}
+
+/*
+ * ioc_frame_unwind - frame unwinds only from here 
+ *
+ * @frame: call frame to unwind
+ *
+ * to be used only by ioc_frame_return(), when a frame has
+ * finished waiting on all pages, required
+ *
+ */
+static void
+ioc_frame_unwind (call_frame_t *frame)
+{
+	ioc_local_t *local = frame->local;
+	ioc_fill_t *fill = NULL, *next = NULL;
+	int32_t count = 0;
+	struct iovec *vector = NULL;
+	int32_t copied = 0;
+	dict_t *refs = NULL;
+	struct stat stbuf = {0,};
+	int32_t op_ret = 0;
+
+	//  ioc_local_lock (local);
+	refs = get_new_dict ();
+
+	frame->local = NULL;
+
+	if (list_empty (&local->fill_list)) {
+		gf_log (frame->this->name, GF_LOG_DEBUG,
+			"frame(%p) has 0 entries in local->fill_list "
+			"(offset = %"PRId64" && size = %"GF_PRI_SIZET")",
+			frame, local->offset, local->size);
+	}
+
+	list_for_each_entry (fill, &local->fill_list, list) {
+		count += fill->count;
+	}
+
+	vector = CALLOC (count, sizeof (*vector));
+	ERR_ABORT (vector);
+  
+	list_for_each_entry_safe (fill, next, &local->fill_list, list) {
+		memcpy (((char *)vector) + copied,
+			fill->vector,
+			fill->count * sizeof (*vector));
+    
+		copied += (fill->count * sizeof (*vector));
+
+		dict_copy (fill->refs, refs);
+
+		list_del (&fill->list);
+		dict_unref (fill->refs);
+		free (fill->vector);
+		free (fill);
+	}
+  
+	frame->root->rsp_refs = dict_ref (refs);
+  
+	op_ret = iov_length (vector, count);
+	gf_log (frame->this->name, GF_LOG_DEBUG,
+		"frame(%p) unwinding with op_ret=%d", frame, op_ret);
+
+	//  ioc_local_unlock (local);
+
+	STACK_UNWIND (frame,
+		      op_ret,
+		      local->op_errno,
+		      vector,
+		      count,
+		      &stbuf);
+
+	dict_unref (refs);
+    
+	pthread_mutex_destroy (&local->local_lock);
+	free (local);
+	free (vector);
+
+	return;
+}
+
+/*
+ * ioc_frame_return -
+ * @frame:
+ *
+ * to be called only when a frame is waiting on an in-transit page
+ */
+void
+ioc_frame_return (call_frame_t *frame)
+{
+	ioc_local_t *local = frame->local;
+	int32_t wait_count;
+	assert (local->wait_count > 0);
+
+	ioc_local_lock (local);
+	{
+		wait_count = --local->wait_count;
+	}
+	ioc_local_unlock (local);
+
+	if (!wait_count) {
+		ioc_frame_unwind (frame);
+	} 
+
+	return;
+}
+
+/* 
+ * ioc_page_wakeup -
+ * @page:
+ *
+ * to be called only when a frame is waiting on an in-transit page
+ */
+ioc_waitq_t *
+ioc_page_wakeup (ioc_page_t *page)
+{
+	ioc_waitq_t *waitq = NULL, *trav = NULL;
+	call_frame_t *frame = NULL;
+
+	waitq = page->waitq;
+	page->waitq = NULL;
+
+	trav = waitq;
+	page->ready = 1;
+
+	gf_log (page->inode->table->xl->name, GF_LOG_DEBUG,
+		"page is %p && waitq = %p", page, waitq);
+  
+	for (trav = waitq; trav; trav = trav->next) {
+		frame = trav->data; 
+		ioc_frame_fill (page, frame, trav->pending_offset, 
+				trav->pending_size);
+	}
+	
+	return waitq;
+}
+
+
+/*
+ * ioc_page_error -
+ * @page:
+ * @op_ret:
+ * @op_errno:
+ *
+ */
+ioc_waitq_t *
+ioc_page_error (ioc_page_t *page,
+		int32_t op_ret,
+		int32_t op_errno)
+{
+	ioc_waitq_t *waitq = NULL, *trav = NULL;
+	call_frame_t *frame = NULL;
+	int64_t ret = 0;
+	ioc_table_t *table = NULL;
+	ioc_local_t *local = NULL;
+
+	waitq = page->waitq;
+	page->waitq = NULL;
+  
+	gf_log (page->inode->table->xl->name, GF_LOG_DEBUG,
+		"page error for page = %p & waitq = %p", page, waitq);
+
+	for (trav = waitq; trav; trav = trav->next) {
+
+		frame = trav->data;
+
+		local = frame->local;
+		ioc_local_lock (local);
+		{
+			if (local->op_ret != -1) {
+				local->op_ret = op_ret;
+				local->op_errno = op_errno;
+			}
+		}
+		ioc_local_unlock (local);
+	}
+
+	table = page->inode->table;
+	ret = ioc_page_destroy (page);
+
+	if (ret != -1) {
+		table->cache_used -= ret;
+	}
+
+	return waitq;
+}
diff --git a/xlators/performance/io-threads/Makefile.am b/xlators/performance/io-threads/Makefile.am
new file mode 100644
index 00000000000..d471a3f9243
--- /dev/null
+++ b/xlators/performance/io-threads/Makefile.am
@@ -0,0 +1,3 @@
+SUBDIRS = src
+
+CLEANFILES = 
diff --git a/xlators/performance/io-threads/src/Makefile.am b/xlators/performance/io-threads/src/Makefile.am
new file mode 100644
index 00000000000..38dea3eb7fc
--- /dev/null
+++ b/xlators/performance/io-threads/src/Makefile.am
@@ -0,0 +1,14 @@
+xlator_LTLIBRARIES = io-threads.la
+xlatordir = $(libdir)/glusterfs/$(PACKAGE_VERSION)/xlator/performance
+
+io_threads_la_LDFLAGS = -module -avoidversion 
+
+io_threads_la_SOURCES = io-threads.c
+io_threads_la_LIBADD = $(top_builddir)/libglusterfs/src/libglusterfs.la
+
+noinst_HEADERS = io-threads.h
+
+AM_CFLAGS = -fPIC -D_FILE_OFFSET_BITS=64 -D_GNU_SOURCE -Wall -D$(GF_HOST_OS)\
+	-I$(top_srcdir)/libglusterfs/src -shared -nostartfiles $(GF_CFLAGS)
+
+CLEANFILES = 
diff --git a/xlators/performance/io-threads/src/io-threads.c b/xlators/performance/io-threads/src/io-threads.c
new file mode 100644
index 00000000000..5acdd627da4
--- /dev/null
+++ b/xlators/performance/io-threads/src/io-threads.c
@@ -0,0 +1,1254 @@
+/*
+  Copyright (c) 2006, 2007, 2008, 2009 Z RESEARCH, Inc. <http://www.zresearch.com>
+  This file is part of GlusterFS.
+
+  GlusterFS is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published
+  by the Free Software Foundation; either version 3 of the License,
+  or (at your option) any later version.
+
+  GlusterFS is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see
+  <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef _CONFIG_H
+#define _CONFIG_H
+#include "config.h"
+#endif
+
+#include "call-stub.h"
+#include "glusterfs.h"
+#include "logging.h"
+#include "dict.h"
+#include "xlator.h"
+#include "io-threads.h"
+
+static void
+iot_queue (iot_worker_t *worker,
+           call_stub_t *stub);
+
+static call_stub_t *
+iot_dequeue (iot_worker_t *worker);
+
+static iot_worker_t * 
+iot_schedule (iot_conf_t *conf,
+              iot_file_t *file,
+              ino_t ino)
+{
+	int32_t cnt = (ino % conf->thread_count);
+	iot_worker_t *trav = conf->workers.next;
+
+	for (; cnt; cnt--)
+		trav = trav->next;
+  
+	if (file)
+		file->worker = trav;
+	trav->fd_count++;
+	return trav;
+}
+
+int32_t
+iot_open_cbk (call_frame_t *frame,
+              void *cookie,
+              xlator_t *this,
+              int32_t op_ret,
+              int32_t op_errno,
+              fd_t *fd)
+{
+	iot_conf_t *conf = this->private;
+
+	if (op_ret >= 0) {
+		iot_file_t *file = CALLOC (1, sizeof (*file));
+		ERR_ABORT (file);
+
+		iot_schedule (conf, file, fd->inode->ino);
+		file->fd = fd;
+
+		fd_ctx_set (fd, this, (uint64_t)(long)file);
+
+		pthread_mutex_lock (&conf->files_lock);
+		file->next = &conf->files;
+		file->prev = file->next->prev;
+		file->next->prev = file;
+		file->prev->next = file;
+		pthread_mutex_unlock (&conf->files_lock);
+	}
+	STACK_UNWIND (frame, op_ret, op_errno, fd);
+	return 0;
+}
+
+int32_t
+iot_open (call_frame_t *frame,
+          xlator_t *this,
+          loc_t *loc,
+          int32_t flags,
+	  fd_t *fd)
+{
+	STACK_WIND (frame,
+		    iot_open_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->open,
+		    loc,
+		    flags,
+		    fd);
+	return 0;
+}
+
+
+int32_t
+iot_create_cbk (call_frame_t *frame,
+		void *cookie,
+		xlator_t *this,
+		int32_t op_ret,
+		int32_t op_errno,
+		fd_t *fd,
+		inode_t *inode,
+		struct stat *stbuf)
+{
+	iot_conf_t *conf = this->private;
+
+	if (op_ret >= 0) {
+		iot_file_t *file = CALLOC (1, sizeof (*file));
+		ERR_ABORT (file);
+
+		iot_schedule (conf, file, fd->inode->ino);
+		file->fd = fd;
+
+		fd_ctx_set (fd, this, (uint64_t)(long)file);
+
+		pthread_mutex_lock (&conf->files_lock);
+		file->next = &conf->files;
+		file->prev = file->next->prev;
+		file->next->prev = file;
+		file->prev->next = file;
+		pthread_mutex_unlock (&conf->files_lock);
+	}
+	STACK_UNWIND (frame, op_ret, op_errno, fd, inode, stbuf);
+	return 0;
+}
+
+int32_t
+iot_create (call_frame_t *frame,
+            xlator_t *this,
+	    loc_t *loc,
+            int32_t flags,
+            mode_t mode,
+	    fd_t *fd)
+{
+	STACK_WIND (frame,
+		    iot_create_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->create,
+		    loc,
+		    flags,
+		    mode,
+		    fd);
+	return 0;
+}
+
+
+
+int32_t
+iot_readv_cbk (call_frame_t *frame,
+               void *cookie,
+               xlator_t *this,
+               int32_t op_ret,
+               int32_t op_errno,
+               struct iovec *vector,
+               int32_t count,
+	       struct stat *stbuf)
+{
+	iot_local_t *local = frame->local;
+
+	local->frame_size = 0; //iov_length (vector, count);
+
+	STACK_UNWIND (frame, op_ret, op_errno, vector, count, stbuf);
+
+	return 0;
+}
+
+static int32_t
+iot_readv_wrapper (call_frame_t *frame,
+                   xlator_t *this,
+                   fd_t *fd,
+                   size_t size,
+                   off_t offset)
+{
+	STACK_WIND (frame,
+		    iot_readv_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->readv,
+		    fd,
+		    size,
+		    offset);
+	return 0;
+}
+
+int32_t
+iot_readv (call_frame_t *frame,
+           xlator_t *this,
+           fd_t *fd,
+           size_t size,
+           off_t offset)
+{
+	call_stub_t *stub;
+	iot_local_t *local = NULL;
+	iot_file_t *file = NULL;
+	iot_worker_t *worker = NULL;
+	uint64_t tmp_file = 0;
+
+	if (fd_ctx_get (fd, this, &tmp_file)) {
+		gf_log (this->name, GF_LOG_ERROR, 
+			"fd context is NULL, returning EBADFD");
+		STACK_UNWIND (frame, -1, EBADFD);
+		return 0;
+	}
+
+	file = (iot_file_t *)(long)tmp_file;
+	worker = file->worker;
+
+	local = CALLOC (1, sizeof (*local));
+	ERR_ABORT (local);
+	frame->local = local;
+  
+	stub = fop_readv_stub (frame, 
+			       iot_readv_wrapper,
+			       fd,
+			       size,
+			       offset);
+	if (!stub) {
+		gf_log (this->name, GF_LOG_ERROR, 
+			"cannot get readv call stub");
+		STACK_UNWIND (frame, -1, ENOMEM, NULL, 0);
+		return 0;
+	}
+
+	iot_queue (worker, stub);
+
+	return 0;
+}
+
+int32_t
+iot_flush_cbk (call_frame_t *frame,
+               void *cookie,
+               xlator_t *this,
+               int32_t op_ret,
+               int32_t op_errno)
+{
+	STACK_UNWIND (frame, op_ret, op_errno);
+	return 0;
+}
+
+static int32_t
+iot_flush_wrapper (call_frame_t *frame,
+                   xlator_t *this,
+                   fd_t *fd)
+{
+	STACK_WIND (frame,
+		    iot_flush_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->flush,
+		    fd);
+	return 0;
+}
+
+int32_t
+iot_flush (call_frame_t *frame,
+           xlator_t *this,
+           fd_t *fd)
+{
+	call_stub_t *stub;
+	iot_local_t *local = NULL;
+	iot_file_t *file = NULL;
+	iot_worker_t *worker = NULL;
+	uint64_t tmp_file = 0;
+
+	if (fd_ctx_get (fd, this, &tmp_file)) {
+		gf_log (this->name, GF_LOG_ERROR, 
+			"fd context is NULL, returning EBADFD");
+		STACK_UNWIND (frame, -1, EBADFD);
+		return 0;
+	}
+
+	file = (iot_file_t *)(long)tmp_file;
+	worker = file->worker;
+
+	local = CALLOC (1, sizeof (*local));
+	ERR_ABORT (local);
+
+	frame->local = local;
+  
+	stub = fop_flush_stub (frame,
+			       iot_flush_wrapper,
+			       fd);
+	if (!stub) {
+		gf_log (this->name, GF_LOG_ERROR, "cannot get flush_cbk call stub");
+		STACK_UNWIND (frame, -1, ENOMEM);
+		return 0;
+	}
+	iot_queue (worker, stub);
+
+	return 0;
+}
+
+int32_t
+iot_fsync_cbk (call_frame_t *frame,
+               void *cookie,
+               xlator_t *this,
+               int32_t op_ret,
+               int32_t op_errno)
+{
+	STACK_UNWIND (frame, op_ret, op_errno);
+	return 0;
+}
+
+static int32_t
+iot_fsync_wrapper (call_frame_t *frame,
+                   xlator_t *this,
+                   fd_t *fd,
+                   int32_t datasync)
+{
+	STACK_WIND (frame,
+		    iot_fsync_cbk,
+		    FIRST_CHILD (this),
+		    FIRST_CHILD (this)->fops->fsync,
+		    fd,
+		    datasync);
+	return 0;
+}
+
+int32_t
+iot_fsync (call_frame_t *frame,
+           xlator_t *this,
+           fd_t *fd,
+           int32_t datasync)
+{
+	call_stub_t *stub;
+	iot_local_t *local = NULL;
+	iot_file_t *file = NULL;
+	iot_worker_t *worker = NULL;
+	uint64_t tmp_file = 0;
+
+	if (fd_ctx_get (fd, this, &tmp_file)) {
+		gf_log (this->name, GF_LOG_ERROR, 
+			"fd context is NULL, returning EBADFD");
+		STACK_UNWIND (frame, -1, EBADFD);
+		return 0;
+	}
+
+	file = (iot_file_t *)(long)tmp_file;
+	worker = file->worker;
+
+	local = CALLOC (1, sizeof (*local));
+	ERR_ABORT (local);
+
+	frame->local = local;
+  
+	stub = fop_fsync_stub (frame,
+			       iot_fsync_wrapper,
+			       fd,
+			       datasync);
+	if (!stub) {
+		gf_log (this->name, GF_LOG_ERROR, "cannot get fsync_cbk call stub");
+		STACK_UNWIND (frame, -1, ENOMEM);
+		return 0;
+	}
+	iot_queue (worker, stub);
+
+	return 0;
+}
+
+int32_t
+iot_writev_cbk (call_frame_t *frame,
+                void *cookie,
+                xlator_t *this,
+                int32_t op_ret,
+                int32_t op_errno,
+		struct stat *stbuf)
+{
+	iot_local_t *local = frame->local;
+
+	local->frame_size = 0; /* hehe, caught me! */
+
+	STACK_UNWIND (frame, op_ret, op_errno, stbuf);
+	return 0;
+}
+
+static int32_t
+iot_writev_wrapper (call_frame_t *frame,
+                    xlator_t *this,
+                    fd_t *fd,
+                    struct iovec *vector,
+                    int32_t count,
+                    off_t offset)
+{
+	STACK_WIND (frame,
+		    iot_writev_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->writev,
+		    fd,
+		    vector,
+		    count,
+		    offset);
+	return 0;
+}
+
+int32_t
+iot_writev (call_frame_t *frame,
+            xlator_t *this,
+            fd_t *fd,
+            struct iovec *vector,
+            int32_t count,
+            off_t offset)
+{
+	call_stub_t *stub;
+	iot_local_t *local = NULL;
+	iot_file_t *file = NULL;
+	iot_worker_t *worker = NULL;
+	uint64_t tmp_file = 0;
+
+	if (fd_ctx_get (fd, this, &tmp_file)) {
+		gf_log (this->name, GF_LOG_ERROR, 
+			"fd context is NULL, returning EBADFD");
+		STACK_UNWIND (frame, -1, EBADFD);
+		return 0;
+	}
+
+	file = (iot_file_t *)(long)tmp_file;
+	worker = file->worker;
+
+	local = CALLOC (1, sizeof (*local));
+	ERR_ABORT (local);
+
+	if (frame->root->req_refs)
+		local->frame_size = dict_serialized_length (frame->root->req_refs);
+	else
+		local->frame_size = iov_length (vector, count);
+	frame->local = local;
+  
+	stub = fop_writev_stub (frame, iot_writev_wrapper,
+				fd, vector, count, offset);
+
+	if (!stub) {
+		gf_log (this->name, GF_LOG_ERROR, "cannot get writev call stub");
+		STACK_UNWIND (frame, -1, ENOMEM);
+		return 0;
+	}
+
+	iot_queue (worker, stub);
+
+	return 0;
+}
+
+
+int32_t
+iot_lk_cbk (call_frame_t *frame,
+            void *cookie,
+            xlator_t *this,
+            int32_t op_ret,
+            int32_t op_errno,
+            struct flock *flock)
+{
+	STACK_UNWIND (frame, op_ret, op_errno, flock);
+	return 0;
+}
+
+
+static int32_t
+iot_lk_wrapper (call_frame_t *frame,
+                xlator_t *this,
+                fd_t *fd,
+                int32_t cmd,
+                struct flock *flock)
+{
+	STACK_WIND (frame,
+		    iot_lk_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->lk,
+		    fd,
+		    cmd,
+		    flock);
+	return 0;
+}
+
+
+int32_t
+iot_lk (call_frame_t *frame,
+	xlator_t *this,
+	fd_t *fd,
+	int32_t cmd,
+	struct flock *flock)
+{
+	call_stub_t *stub;
+	iot_local_t *local = NULL;
+	iot_file_t *file = NULL;
+	iot_worker_t *worker = NULL;
+	uint64_t tmp_file = 0;
+
+	if (fd_ctx_get (fd, this, &tmp_file)) {
+		gf_log (this->name, GF_LOG_ERROR, 
+			"fd context is NULL, returning EBADFD");
+		STACK_UNWIND (frame, -1, EBADFD);
+		return 0;
+	}
+
+	file = (iot_file_t *)(long)tmp_file;
+	worker = file->worker;
+
+	local = CALLOC (1, sizeof (*local));
+	ERR_ABORT (local);
+	frame->local = local;
+
+	stub = fop_lk_stub (frame, iot_lk_wrapper,
+			    fd, cmd, flock);
+
+	if (!stub) {
+		gf_log (this->name, GF_LOG_ERROR, "cannot get fop_lk call stub");
+		STACK_UNWIND (frame, -1, ENOMEM, NULL);
+		return 0;
+	}
+    
+	iot_queue (worker, stub);
+
+	return 0;
+}
+
+
+int32_t 
+iot_stat_cbk (call_frame_t *frame,
+              void *cookie,
+              xlator_t *this,
+              int32_t op_ret,
+              int32_t op_errno,
+              struct stat *buf)
+{
+	STACK_UNWIND (frame, op_ret, op_errno, buf);
+	return 0;
+}
+
+
+static int32_t 
+iot_stat_wrapper (call_frame_t *frame,
+                  xlator_t *this,
+                  loc_t *loc)
+{
+	STACK_WIND (frame,
+		    iot_stat_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->stat,
+		    loc);
+	return 0;
+}
+
+int32_t 
+iot_stat (call_frame_t *frame,
+          xlator_t *this,
+          loc_t *loc)
+{
+	call_stub_t *stub;
+	iot_local_t *local = NULL;
+	iot_worker_t *worker = NULL;
+	iot_conf_t *conf;
+	fd_t *fd = NULL;
+
+	conf = this->private;
+
+	local = CALLOC (1, sizeof (*local));
+	ERR_ABORT (local);
+	frame->local = local;
+
+	fd = fd_lookup (loc->inode, frame->root->pid);
+
+	if (fd == NULL) {
+		STACK_WIND(frame,
+			   iot_stat_cbk,
+			   FIRST_CHILD(this),
+			   FIRST_CHILD(this)->fops->stat,
+			   loc);
+		return 0;
+	} 
+  
+	fd_unref (fd);
+
+	worker = iot_schedule (conf, NULL, loc->inode->ino);
+
+	stub = fop_stat_stub (frame,
+			      iot_stat_wrapper,
+			      loc);
+	if (!stub) {
+		gf_log (this->name, GF_LOG_ERROR, "cannot get fop_stat call stub");
+		STACK_UNWIND (frame, -1, ENOMEM, NULL);
+		return 0;
+	}
+	iot_queue (worker, stub);
+
+	return 0;
+}
+
+
+int32_t 
+iot_fstat_cbk (call_frame_t *frame,
+               void *cookie,
+               xlator_t *this,
+               int32_t op_ret,
+               int32_t op_errno,
+               struct stat *buf)
+{
+	STACK_UNWIND (frame, op_ret, op_errno, buf);
+	return 0;
+}
+
+static int32_t 
+iot_fstat_wrapper (call_frame_t *frame,
+                   xlator_t *this,
+                   fd_t *fd)
+{
+	STACK_WIND (frame,
+		    iot_fstat_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->fstat,
+		    fd);
+	return 0;
+}
+
+int32_t 
+iot_fstat (call_frame_t *frame,
+           xlator_t *this,
+           fd_t *fd)
+{
+	call_stub_t *stub;
+	iot_local_t *local = NULL;
+	iot_file_t *file = NULL;
+	iot_worker_t *worker = NULL;
+	uint64_t tmp_file = 0;
+
+	if (fd_ctx_get (fd, this, &tmp_file)) {
+		gf_log (this->name, GF_LOG_ERROR, 
+			"fd context is NULL, returning EBADFD");
+		STACK_UNWIND (frame, -1, EBADFD);
+		return 0;
+	}
+
+	file = (iot_file_t *)(long)tmp_file;
+	worker = file->worker;
+
+	local = CALLOC (1, sizeof (*local));
+	ERR_ABORT (local);
+	frame->local = local;
+	stub = fop_fstat_stub (frame,
+			       iot_fstat_wrapper,
+			       fd);
+	if (!stub) {
+		gf_log (this->name, GF_LOG_ERROR, "cannot get fop_fstat call stub");
+		STACK_UNWIND (frame, -1, ENOMEM, NULL);
+		return 0;
+	}
+
+	iot_queue (worker, stub);
+
+	return 0;
+}
+
+int32_t 
+iot_truncate_cbk (call_frame_t *frame,
+                  void *cookie,
+                  xlator_t *this,
+                  int32_t op_ret,
+                  int32_t op_errno,
+                  struct stat *buf)
+{
+	STACK_UNWIND (frame, op_ret, op_errno, buf);
+	return 0;
+}
+
+static int32_t 
+iot_truncate_wrapper (call_frame_t *frame,
+                      xlator_t *this,
+                      loc_t *loc,
+                      off_t offset)
+{
+	STACK_WIND (frame,
+		    iot_truncate_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->truncate,
+		    loc,
+		    offset);
+	return 0;
+}
+
+int32_t 
+iot_truncate (call_frame_t *frame,
+              xlator_t *this,
+              loc_t *loc,
+              off_t offset)
+{
+	call_stub_t *stub;
+	iot_local_t *local = NULL;
+	iot_worker_t *worker = NULL;
+	iot_conf_t *conf;
+	fd_t *fd = NULL;
+  
+	conf = this->private;
+	local = CALLOC (1, sizeof (*local));
+	ERR_ABORT (local);
+	frame->local = local;
+
+	fd = fd_lookup (loc->inode, frame->root->pid);
+
+	if (fd == NULL) {
+		STACK_WIND(frame,
+			   iot_truncate_cbk,
+			   FIRST_CHILD(this),
+			   FIRST_CHILD(this)->fops->truncate,
+			   loc,
+			   offset);
+		return 0;
+	} 
+  
+	fd_unref (fd);
+
+	worker = iot_schedule (conf, NULL, loc->inode->ino);
+
+	stub = fop_truncate_stub (frame,
+				  iot_truncate_wrapper,
+				  loc,
+				  offset);
+	if (!stub) {
+		gf_log (this->name, GF_LOG_ERROR, "cannot get fop_stat call stub");
+		STACK_UNWIND (frame, -1, ENOMEM, NULL);
+		return 0;
+	}
+	iot_queue (worker, stub);
+
+	return 0;
+}
+
+int32_t 
+iot_ftruncate_cbk (call_frame_t *frame,
+                   void *cookie,
+                   xlator_t *this,
+                   int32_t op_ret,
+                   int32_t op_errno,
+                   struct stat *buf)
+{
+	STACK_UNWIND (frame, op_ret, op_errno, buf);
+	return 0;
+}
+
+static int32_t 
+iot_ftruncate_wrapper (call_frame_t *frame,
+                       xlator_t *this,
+                       fd_t *fd,
+                       off_t offset)
+{
+	STACK_WIND (frame,
+		    iot_ftruncate_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->ftruncate,
+		    fd,
+		    offset);
+	return 0;
+}
+
+int32_t 
+iot_ftruncate (call_frame_t *frame,
+               xlator_t *this,
+               fd_t *fd,
+               off_t offset)
+{
+	call_stub_t *stub;
+	iot_local_t *local = NULL;
+	iot_file_t *file = NULL;
+	iot_worker_t *worker = NULL;
+	uint64_t tmp_file = 0;
+
+	if (fd_ctx_get (fd, this, &tmp_file)) {
+		gf_log (this->name, GF_LOG_ERROR, 
+			"fd context is NULL, returning EBADFD");
+		STACK_UNWIND (frame, -1, EBADFD);
+		return 0;
+	}
+
+	file = (iot_file_t *)(long)tmp_file;
+	worker = file->worker;
+
+	local = CALLOC (1, sizeof (*local));
+	ERR_ABORT (local);
+	frame->local = local;
+
+	stub = fop_ftruncate_stub (frame,
+				   iot_ftruncate_wrapper,
+				   fd,
+				   offset);
+	if (!stub) {
+		gf_log (this->name, GF_LOG_ERROR, "cannot get fop_ftruncate call stub");
+		STACK_UNWIND (frame, -1, ENOMEM, NULL);
+		return 0;
+	}
+	iot_queue (worker, stub);
+
+	return 0;
+}
+
+int32_t 
+iot_utimens_cbk (call_frame_t *frame,
+                 void *cookie,
+                 xlator_t *this,
+                 int32_t op_ret,
+                 int32_t op_errno,
+                 struct stat *buf)
+{
+	STACK_UNWIND (frame, op_ret, op_errno, buf);
+	return 0;
+}
+
+static int32_t 
+iot_utimens_wrapper (call_frame_t *frame,
+                     xlator_t *this,
+                     loc_t *loc,
+                     struct timespec tv[2])
+{
+	STACK_WIND (frame,
+		    iot_utimens_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->utimens,
+		    loc,
+		    tv);
+  
+	return 0;
+}
+
+int32_t 
+iot_utimens (call_frame_t *frame,
+             xlator_t *this,
+             loc_t *loc,
+             struct timespec tv[2])
+{
+	call_stub_t *stub;
+	iot_local_t *local = NULL;
+	iot_worker_t *worker = NULL;
+	iot_conf_t *conf;
+	fd_t *fd = NULL;
+  
+	conf = this->private;
+
+	local = CALLOC (1, sizeof (*local));
+	ERR_ABORT (local);
+	frame->local = local;
+  
+	fd = fd_lookup (loc->inode, frame->root->pid);
+
+	if (fd == NULL) {
+		STACK_WIND(frame,
+			   iot_utimens_cbk,
+			   FIRST_CHILD(this),
+			   FIRST_CHILD(this)->fops->utimens,
+			   loc,
+			   tv);
+		return 0;
+	} 
+  
+	fd_unref (fd);
+
+	worker = iot_schedule (conf, NULL, loc->inode->ino);
+
+	stub = fop_utimens_stub (frame,
+				 iot_utimens_wrapper,
+				 loc,
+				 tv);
+	if (!stub) {
+		gf_log (this->name, GF_LOG_ERROR, "cannot get fop_utimens call stub");
+		STACK_UNWIND (frame, -1, ENOMEM, NULL);
+		return 0;
+	}
+	iot_queue (worker, stub);
+
+	return 0;
+}
+
+
+int32_t 
+iot_checksum_cbk (call_frame_t *frame,
+		  void *cookie,
+		  xlator_t *this,
+		  int32_t op_ret,
+		  int32_t op_errno,
+		  uint8_t *file_checksum,
+		  uint8_t *dir_checksum)
+{
+	STACK_UNWIND (frame, op_ret, op_errno, file_checksum, dir_checksum);
+	return 0;
+}
+
+static int32_t 
+iot_checksum_wrapper (call_frame_t *frame,
+		      xlator_t *this,
+		      loc_t *loc,
+		      int32_t flags)
+{
+	STACK_WIND (frame,
+		    iot_checksum_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->checksum,
+		    loc,
+		    flags);
+  
+	return 0;
+}
+
+int32_t 
+iot_checksum (call_frame_t *frame,
+	      xlator_t *this,
+	      loc_t *loc,
+	      int32_t flags)
+{
+	call_stub_t *stub = NULL;
+	iot_local_t *local = NULL;
+	iot_worker_t *worker = NULL;
+	iot_conf_t *conf = NULL;
+  
+	conf = this->private;
+
+	local = CALLOC (1, sizeof (*local));
+	frame->local = local;
+
+	worker = iot_schedule (conf, NULL, conf->misc_thread_index++);
+
+	stub = fop_checksum_stub (frame,
+				  iot_checksum_wrapper,
+				  loc,
+				  flags);
+	if (!stub) {
+		gf_log (this->name, GF_LOG_ERROR, "cannot get fop_checksum call stub");
+		STACK_UNWIND (frame, -1, ENOMEM, NULL, NULL);
+		return 0;
+	}
+	iot_queue (worker, stub);
+
+	return 0;
+}
+
+
+int32_t 
+iot_unlink_cbk (call_frame_t *frame,
+		void *cookie,
+		xlator_t *this,
+		int32_t op_ret,
+		int32_t op_errno)
+{
+	STACK_UNWIND (frame, op_ret, op_errno);
+	return 0;
+}
+
+static int32_t 
+iot_unlink_wrapper (call_frame_t *frame,
+		    xlator_t *this,
+		    loc_t *loc)
+{
+	STACK_WIND (frame,
+		    iot_unlink_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->unlink,
+		    loc);
+  
+	return 0;
+}
+
+int32_t 
+iot_unlink (call_frame_t *frame,
+	    xlator_t *this,
+	    loc_t *loc)
+{
+	call_stub_t *stub = NULL;
+	iot_local_t *local = NULL;
+	iot_worker_t *worker = NULL;
+	iot_conf_t *conf = NULL;
+
+	conf = this->private;
+
+	local = CALLOC (1, sizeof (*local));
+	frame->local = local;
+
+	worker = iot_schedule (conf, NULL, conf->misc_thread_index++);
+
+	stub = fop_unlink_stub (frame, iot_unlink_wrapper, loc);
+	if (!stub) {
+		gf_log (this->name, GF_LOG_ERROR, "cannot get fop_unlink call stub");
+		STACK_UNWIND (frame, -1, ENOMEM);
+		return 0;
+	}
+	iot_queue (worker, stub);
+
+	return 0;
+}
+
+int32_t
+iot_release (xlator_t *this,
+	     fd_t *fd)
+{
+	iot_file_t *file = NULL;
+	iot_conf_t *conf = NULL;
+	uint64_t tmp_file = 0;
+	int ret = 0;
+
+	conf = this->private;
+	ret = fd_ctx_del (fd, this, &tmp_file);
+	if (ret)
+		return 0;
+
+	file = (iot_file_t *)(long)tmp_file;
+
+	pthread_mutex_lock (&conf->files_lock);
+	{
+		(file->prev)->next = file->next;
+		(file->next)->prev = file->prev;
+	}
+	pthread_mutex_unlock (&conf->files_lock);
+
+	FREE (file);
+	return 0;
+}
+
+
+static void
+iot_queue (iot_worker_t *worker,
+           call_stub_t *stub)
+{
+	iot_queue_t *queue;
+	iot_conf_t *conf = worker->conf;
+	iot_local_t *local = stub->frame->local;
+	size_t frame_size = local->frame_size;
+
+	queue = CALLOC (1, sizeof (*queue));
+	ERR_ABORT (queue);
+	queue->stub = stub;
+
+	pthread_mutex_lock (&conf->lock);
+
+	/*
+	  while (worker->queue_size >= worker->queue_limit)
+	  pthread_cond_wait (&worker->q_cond, &worker->lock);
+	*/
+	if (conf->cache_size) {
+		while (frame_size && (conf->current_size >= conf->cache_size))
+			pthread_cond_wait (&conf->q_cond, &conf->lock);
+	}
+
+	queue->next = &worker->queue;
+	queue->prev = worker->queue.prev;
+
+	queue->next->prev = queue;
+	queue->prev->next = queue;
+
+	/* dq_cond */
+	worker->queue_size++;
+	worker->q++;
+
+	conf->current_size += local->frame_size;
+
+	pthread_cond_broadcast (&worker->dq_cond);
+
+	pthread_mutex_unlock (&conf->lock);
+}
+
+static call_stub_t *
+iot_dequeue (iot_worker_t *worker)
+{
+	call_stub_t *stub = NULL;
+	iot_queue_t *queue = NULL;
+	iot_conf_t *conf = worker->conf;
+	iot_local_t *local = NULL;
+
+
+	pthread_mutex_lock (&conf->lock);
+
+	while (!worker->queue_size)
+		/*
+		  pthread_cond_wait (&worker->dq_cond, &worker->lock);
+		*/
+		pthread_cond_wait (&worker->dq_cond, &conf->lock);
+
+	queue = worker->queue.next;
+
+	queue->next->prev = queue->prev;
+	queue->prev->next = queue->next;
+
+	stub = queue->stub;
+	local = stub->frame->local;
+
+	worker->queue_size--;
+	worker->dq++;
+
+	/* q_cond */
+	conf->current_size -= local->frame_size;
+
+	pthread_cond_broadcast (&conf->q_cond);
+
+	pthread_mutex_unlock (&conf->lock);
+
+	FREE (queue);
+
+	return stub;
+}
+
+static void *
+iot_worker (void *arg)
+{
+	iot_worker_t *worker = arg;
+
+	while (1) {
+		call_stub_t *stub;
+
+		stub = iot_dequeue (worker);
+		call_resume (stub);
+	}
+}
+
+#if 0
+static void *
+iot_reply (void *arg)
+{
+	iot_worker_t *reply = arg;
+
+	while (1) {
+		call_stub_t *stub;
+
+		stub = iot_dequeue (reply);
+		FREE (stub->frame->local);
+		stub->frame->local = NULL;
+		call_resume (stub);
+	}
+}
+#endif
+
+static void
+workers_init (iot_conf_t *conf)
+{
+	int i;
+
+	conf->workers.next = &conf->workers;
+	conf->workers.prev = &conf->workers;
+
+	for (i=0; i<conf->thread_count; i++) {
+
+		iot_worker_t *worker = CALLOC (1, sizeof (*worker));
+		ERR_ABORT (worker);
+
+		worker->next = &conf->workers;
+		worker->prev = conf->workers.prev;
+		worker->next->prev = worker;
+		worker->prev->next = worker;
+
+		worker->queue.next = &worker->queue;
+		worker->queue.prev = &worker->queue;
+
+		/*
+		  pthread_mutex_init (&worker->lock, NULL);
+		  pthread_cond_init (&worker->q_cond, NULL);
+		*/
+		pthread_cond_init (&worker->dq_cond, NULL);
+
+		/*
+		  worker->queue_limit = conf->queue_limit;
+		*/
+
+		worker->conf = conf;
+
+		pthread_create (&worker->thread, NULL, iot_worker, worker);
+	}
+}
+
+int32_t 
+init (xlator_t *this)
+{
+	iot_conf_t *conf;
+	dict_t *options = this->options;
+
+	if (!this->children || this->children->next) {
+		gf_log ("io-threads",
+			GF_LOG_ERROR,
+			"FATAL: iot not configured with exactly one child");
+		return -1;
+	}
+
+	if (!this->parents) {
+		gf_log (this->name, GF_LOG_WARNING,
+			"dangling volume. check volfile ");
+	}
+
+	conf = (void *) CALLOC (1, sizeof (*conf));
+	ERR_ABORT (conf);
+
+	conf->thread_count = 1;
+
+	if (dict_get (options, "thread-count")) {
+		conf->thread_count = data_to_int32 (dict_get (options,
+							      "thread-count"));
+		gf_log ("io-threads",
+			GF_LOG_DEBUG,
+			"Using conf->thread_count = %d",
+			conf->thread_count);
+	}
+
+	pthread_mutex_init (&conf->lock, NULL);
+	pthread_cond_init (&conf->q_cond, NULL);
+
+	conf->files.next = &conf->files;
+	conf->files.prev = &conf->files;
+	pthread_mutex_init (&conf->files_lock, NULL);
+
+	workers_init (conf);
+
+	this->private = conf;
+	return 0;
+}
+
+void
+fini (xlator_t *this)
+{
+	iot_conf_t *conf = this->private;
+
+	FREE (conf);
+
+	this->private = NULL;
+	return;
+}
+
+struct xlator_fops fops = {
+	.open        = iot_open,
+	.create      = iot_create,
+	.readv       = iot_readv,
+	.writev      = iot_writev,
+	.flush       = iot_flush,
+	.fsync       = iot_fsync,
+	.lk          = iot_lk,
+	.stat        = iot_stat,
+	.fstat       = iot_fstat,
+	.truncate    = iot_truncate,
+	.ftruncate   = iot_ftruncate,
+	.utimens     = iot_utimens,
+	.checksum    = iot_checksum,
+	.unlink      = iot_unlink,
+};
+
+struct xlator_mops mops = {
+};
+
+struct xlator_cbks cbks = {
+	.release = iot_release,
+};
+
+struct volume_options options[] = {
+	{ .key  = {"thread-count"}, 
+	  .type = GF_OPTION_TYPE_INT, 
+	  .min  = 1, 
+	  .max  = 32
+	},
+	{ .key  = {NULL} },
+};
diff --git a/xlators/performance/io-threads/src/io-threads.h b/xlators/performance/io-threads/src/io-threads.h
new file mode 100644
index 00000000000..6595d3e277b
--- /dev/null
+++ b/xlators/performance/io-threads/src/io-threads.h
@@ -0,0 +1,99 @@
+/*
+   Copyright (c) 2006, 2007, 2008 Z RESEARCH, Inc. <http://www.zresearch.com>
+   This file is part of GlusterFS.
+
+   GlusterFS is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published
+   by the Free Software Foundation; either version 3 of the License,
+   or (at your option) any later version.
+
+   GlusterFS is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see
+   <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __IOT_H
+#define __IOT_H
+
+#ifndef _CONFIG_H
+#define _CONFIG_H
+#include "config.h"
+#endif
+
+
+#include "compat-errno.h"
+#include "glusterfs.h"
+#include "logging.h"
+#include "dict.h"
+#include "xlator.h"
+#include "common-utils.h"
+
+#define min(a,b) ((a)<(b)?(a):(b))
+#define max(a,b) ((a)>(b)?(a):(b))
+
+struct iot_conf;
+struct iot_worker;
+struct iot_queue;
+struct iot_local;
+struct iot_file;
+
+struct iot_local {
+  struct iot_file *file;
+  size_t frame_size;
+};
+
+struct iot_queue {
+  struct iot_queue *next, *prev;
+  call_stub_t *stub;
+};
+
+struct iot_worker {
+  struct iot_worker *next, *prev;
+  struct iot_queue queue;
+  struct iot_conf *conf;
+  int64_t q,dq;
+  pthread_cond_t dq_cond;
+  /*
+    pthread_cond_t q_cond;
+    pthread_mutex_t lock;
+  */
+  int32_t fd_count;
+  int32_t queue_size;
+  /*
+    int32_t queue_limit;
+  */
+  pthread_t thread;
+};
+
+struct iot_file {
+  struct iot_file *next, *prev; /* all open files via this xlator */
+  struct iot_worker *worker;
+  fd_t *fd;
+  int32_t pending_ops;
+};
+
+struct iot_conf {
+  int32_t thread_count;
+  int32_t misc_thread_index;  /* Used to schedule the miscellaneous calls like checksum */
+  struct iot_worker workers;
+  struct iot_file files;
+  pthread_mutex_t files_lock;
+
+  uint64_t cache_size;
+  off_t current_size;
+  pthread_cond_t q_cond;
+  pthread_mutex_t lock;
+};
+
+typedef struct iot_file iot_file_t;
+typedef struct iot_conf iot_conf_t;
+typedef struct iot_local iot_local_t;
+typedef struct iot_worker iot_worker_t;
+typedef struct iot_queue iot_queue_t;
+
+#endif /* __IOT_H */
diff --git a/xlators/performance/read-ahead/Makefile.am b/xlators/performance/read-ahead/Makefile.am
new file mode 100644
index 00000000000..d471a3f9243
--- /dev/null
+++ b/xlators/performance/read-ahead/Makefile.am
@@ -0,0 +1,3 @@
+SUBDIRS = src
+
+CLEANFILES = 
diff --git a/xlators/performance/read-ahead/src/Makefile.am b/xlators/performance/read-ahead/src/Makefile.am
new file mode 100644
index 00000000000..7bb90228227
--- /dev/null
+++ b/xlators/performance/read-ahead/src/Makefile.am
@@ -0,0 +1,14 @@
+xlator_LTLIBRARIES = read-ahead.la
+xlatordir = $(libdir)/glusterfs/$(PACKAGE_VERSION)/xlator/performance
+
+read_ahead_la_LDFLAGS = -module -avoidversion
+
+read_ahead_la_SOURCES = read-ahead.c page.c
+read_ahead_la_LIBADD = $(top_builddir)/libglusterfs/src/libglusterfs.la
+
+noinst_HEADERS = read-ahead.h
+
+AM_CFLAGS = -fPIC -D_FILE_OFFSET_BITS=64 -D_GNU_SOURCE -Wall -D$(GF_HOST_OS)\
+	-I$(top_srcdir)/libglusterfs/src -shared -nostartfiles $(GF_CFLAGS)
+
+CLEANFILES = 
diff --git a/xlators/performance/read-ahead/src/page.c b/xlators/performance/read-ahead/src/page.c
new file mode 100644
index 00000000000..3b8d4d2093e
--- /dev/null
+++ b/xlators/performance/read-ahead/src/page.c
@@ -0,0 +1,487 @@
+/*
+  Copyright (c) 2006, 2007, 2008, 2009 Z RESEARCH, Inc. <http://www.zresearch.com>
+  This file is part of GlusterFS.
+
+  GlusterFS is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published
+  by the Free Software Foundation; either version 3 of the License,
+  or (at your option) any later version.
+
+  GlusterFS is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see
+  <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef _CONFIG_H
+#define _CONFIG_H
+#include "config.h"
+#endif
+
+#include "glusterfs.h"
+#include "logging.h"
+#include "dict.h"
+#include "xlator.h"
+#include "read-ahead.h"
+#include <assert.h>
+
+
+ra_page_t *
+ra_page_get (ra_file_t *file,
+	     off_t offset)
+{
+	ra_page_t *page = NULL;
+	off_t      rounded_offset = 0;
+
+	page = file->pages.next;
+	rounded_offset = floor (offset, file->page_size);
+
+	while (page != &file->pages && page->offset < rounded_offset)
+		page = page->next;
+
+	if (page == &file->pages || page->offset != rounded_offset)
+		page = NULL;
+
+	return page;
+}
+
+
+ra_page_t *
+ra_page_create (ra_file_t *file, off_t offset)
+{
+	ra_page_t *page      = NULL;
+	off_t      rounded_offset = 0;
+	ra_page_t *newpage   = NULL;
+
+	page           = file->pages.next;
+	rounded_offset = floor (offset, file->page_size);
+
+	while (page != &file->pages && page->offset < rounded_offset)
+		page = page->next;
+
+	if (page == &file->pages || page->offset != rounded_offset) {
+		newpage = CALLOC (1, sizeof (*newpage));
+		if (!newpage)
+			return NULL;
+
+		newpage->offset = rounded_offset;
+		newpage->prev = page->prev;
+		newpage->next = page;
+		newpage->file = file;
+		page->prev->next = newpage;
+		page->prev = newpage;
+
+		page = newpage;
+	}
+
+	return page;
+}
+
+
+void
+ra_wait_on_page (ra_page_t *page, call_frame_t *frame)
+{
+	ra_waitq_t *waitq = NULL;
+	ra_local_t *local = NULL;
+
+
+	local = frame->local;
+	waitq = CALLOC (1, sizeof (*waitq));
+	if (!waitq) {
+		gf_log (frame->this->name, GF_LOG_ERROR,
+			"out of memory :(");
+		return;
+	}
+
+	waitq->data = frame;
+	waitq->next = page->waitq;
+	page->waitq = waitq;
+
+	ra_local_lock (local);
+	{
+		local->wait_count++;
+	}
+	ra_local_unlock (local);
+}
+
+
+void
+ra_waitq_return (ra_waitq_t *waitq)
+{
+	ra_waitq_t   *trav = NULL;
+	ra_waitq_t   *next = NULL;
+	call_frame_t *frame = NULL;
+
+	for (trav = waitq; trav; trav = next) {
+		next = trav->next;
+
+		frame = trav->data;
+		ra_frame_return (frame);
+		free (trav);
+	}
+}
+
+
+int
+ra_fault_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+	      int32_t op_ret, int32_t op_errno, struct iovec *vector,
+	      int32_t count, struct stat *stbuf)
+{
+	ra_local_t   *local = NULL;
+	off_t         pending_offset = 0;
+	ra_file_t    *file = NULL;
+	ra_page_t    *page = NULL;
+	off_t         trav_offset = 0;
+	size_t        payload_size = 0;
+	ra_waitq_t   *waitq = NULL;
+	fd_t         *fd = NULL;
+	int           ret = 0;
+	uint64_t      tmp_file = 0;
+
+	local = frame->local;
+	fd  = local->fd;
+
+	ret = fd_ctx_get (fd, this, &tmp_file);
+
+	file = (ra_file_t *)(long)tmp_file;
+	pending_offset = local->pending_offset;
+	trav_offset    = pending_offset;  
+	payload_size   = op_ret;
+
+	ra_file_lock (file);
+	{
+		if (op_ret >= 0)
+			file->stbuf = *stbuf;
+
+		if (op_ret < 0) {
+			page = ra_page_get (file, pending_offset);
+			if (page)
+				waitq = ra_page_error (page, op_ret, op_errno);
+			goto unlock;
+		}
+
+		page = ra_page_get (file, pending_offset);
+		if (!page) {
+			gf_log (this->name, GF_LOG_DEBUG,
+				"wasted copy: %"PRId64"[+%"PRId64"] file=%p", 
+				pending_offset, file->page_size, file);
+			goto unlock;
+		}
+
+		if (page->vector) {
+			dict_unref (page->ref);
+			free (page->vector);
+		}
+
+		page->vector = iov_dup (vector, count);
+		page->count = count;
+		page->ref = dict_ref (frame->root->rsp_refs);
+		page->ready = 1;
+
+		page->size = iov_length (vector, count);
+
+		waitq = ra_page_wakeup (page);
+	}
+unlock:
+	ra_file_unlock (file);
+
+	ra_waitq_return (waitq);
+
+	fd_unref (local->fd);
+
+	free (frame->local);
+	frame->local = NULL;
+
+	STACK_DESTROY (frame->root);
+	return 0;
+}
+
+
+void
+ra_page_fault (ra_file_t *file,
+	       call_frame_t *frame,
+	       off_t offset)
+{
+	call_frame_t *fault_frame = NULL;
+	ra_local_t   *fault_local = NULL;
+    
+	fault_frame = copy_frame (frame);
+	fault_local = CALLOC (1, sizeof (ra_local_t));
+
+	fault_frame->local = fault_local;
+	fault_local->pending_offset = offset;
+	fault_local->pending_size = file->page_size;
+
+	fault_local->fd = fd_ref (file->fd);
+
+	STACK_WIND (fault_frame, ra_fault_cbk,
+		    FIRST_CHILD (fault_frame->this),
+		    FIRST_CHILD (fault_frame->this)->fops->readv,
+		    file->fd, file->page_size, offset);
+	return;
+}
+
+void
+ra_frame_fill (ra_page_t *page, call_frame_t *frame)
+{
+	ra_local_t *local = NULL;
+	ra_fill_t  *fill = NULL;
+	off_t       src_offset = 0;
+	off_t       dst_offset = 0;
+	ssize_t     copy_size = 0;
+	ra_fill_t  *new = NULL;
+
+
+	local = frame->local;
+	fill  = &local->fill;
+
+	if (local->op_ret != -1 && page->size) {
+		if (local->offset > page->offset)
+			src_offset = local->offset - page->offset;
+		else
+			dst_offset = page->offset - local->offset;
+
+		copy_size = min (page->size - src_offset,
+				 local->size - dst_offset);
+
+		if (copy_size < 0) {
+			/* if page contains fewer bytes and the required offset
+			   is beyond the page size in the page */
+			copy_size = src_offset = 0;
+		}
+
+		fill = fill->next;
+		while (fill != &local->fill) {
+			if (fill->offset > page->offset) {
+				break;
+			}
+			fill = fill->next;
+		}
+
+		new = CALLOC (1, sizeof (*new));
+
+		new->offset = page->offset;
+		new->size = copy_size;
+		new->refs = dict_ref (page->ref);
+		new->count = iov_subset (page->vector, page->count,
+					 src_offset, src_offset+copy_size,
+					 NULL);
+		new->vector = CALLOC (new->count, sizeof (struct iovec));
+
+		new->count = iov_subset (page->vector, page->count,
+					 src_offset, src_offset+copy_size,
+					 new->vector);
+
+		new->next = fill;
+		new->prev = new->next->prev;
+		new->next->prev = new;
+		new->prev->next = new;
+
+		local->op_ret += copy_size;
+	}
+}
+
+
+void
+ra_frame_unwind (call_frame_t *frame)
+{
+	ra_local_t   *local = NULL;
+	ra_fill_t    *fill = NULL;
+	int32_t       count = 0;
+	struct iovec *vector;
+	int32_t       copied = 0;
+	dict_t       *refs = NULL;
+	ra_fill_t    *next = NULL;
+	fd_t         *fd = NULL;
+	ra_file_t    *file = NULL;
+	int           ret = 0;
+	uint64_t      tmp_file = 0;
+
+	local = frame->local;
+	fill  = local->fill.next;
+
+	refs  = get_new_dict ();
+
+	frame->local = NULL;
+
+	while (fill != &local->fill) {
+		count += fill->count;
+		fill = fill->next;
+	}
+
+	vector = CALLOC (count, sizeof (*vector));
+
+	fill = local->fill.next;
+
+	while (fill != &local->fill) {
+		next = fill->next;
+
+		memcpy (((char *)vector) + copied, fill->vector,
+			fill->count * sizeof (*vector));
+
+		copied += (fill->count * sizeof (*vector));
+		dict_copy (fill->refs, refs);
+
+		fill->next->prev = fill->prev;
+		fill->prev->next = fill->prev;
+
+		dict_unref (fill->refs);
+		free (fill->vector);
+		free (fill);
+
+		fill = next;
+	}
+
+	frame->root->rsp_refs = dict_ref (refs);
+
+	fd = local->fd;
+	ret = fd_ctx_get (fd, frame->this, &tmp_file);
+	file = (ra_file_t *)(long)tmp_file;
+	
+	STACK_UNWIND (frame, local->op_ret, local->op_errno,
+		      vector, count, &file->stbuf);
+  
+	dict_unref (refs);
+	pthread_mutex_destroy (&local->local_lock);
+	free (local);
+	free (vector);
+
+	return;
+}
+
+/*
+ * ra_frame_return -
+ * @frame:
+ *
+ */
+void
+ra_frame_return (call_frame_t *frame)
+{
+	ra_local_t *local = NULL;
+	int32_t     wait_count = 0;
+
+	local = frame->local;
+	assert (local->wait_count > 0);
+
+	ra_local_lock (local);
+	{
+		wait_count = --local->wait_count;
+	}
+	ra_local_unlock (local);
+
+	if (!wait_count)
+		ra_frame_unwind (frame);
+
+	return;
+}
+
+/* 
+ * ra_page_wakeup -
+ * @page:
+ *
+ */
+ra_waitq_t *
+ra_page_wakeup (ra_page_t *page)
+{
+	ra_waitq_t *waitq = NULL, *trav = NULL;
+	call_frame_t *frame;
+
+	waitq = page->waitq;
+	page->waitq = NULL;
+
+	trav = waitq;
+	for (trav = waitq; trav; trav = trav->next) {
+		frame = trav->data;
+		ra_frame_fill (page, frame);
+	}
+
+	return waitq;
+}
+
+/*
+ * ra_page_purge -
+ * @page:
+ *
+ */
+void
+ra_page_purge (ra_page_t *page)
+{
+	page->prev->next = page->next;
+	page->next->prev = page->prev;
+
+	if (page->ref) {
+		dict_unref (page->ref);
+	}
+	free (page->vector);
+	free (page);
+}
+
+/*
+ * ra_page_error -
+ * @page:
+ * @op_ret:
+ * @op_errno:
+ *
+ */
+ra_waitq_t *
+ra_page_error (ra_page_t *page, int32_t op_ret, int32_t op_errno)
+{
+
+	ra_waitq_t   *waitq = NULL;
+	ra_waitq_t   *trav = NULL;
+	call_frame_t *frame = NULL;
+	ra_local_t   *local = NULL;
+
+	waitq = page->waitq;
+	page->waitq = NULL;
+
+	trav = waitq;
+	for (trav = waitq; trav; trav = trav->next) {
+		frame = trav->data;
+
+		local = frame->local;
+		if (local->op_ret != -1) {
+			local->op_ret   = op_ret;
+			local->op_errno = op_errno;
+		}
+	}
+
+	ra_page_purge (page);
+
+	return waitq;
+}
+
+/* 
+ * ra_file_destroy -
+ * @file:
+ *
+ */
+void
+ra_file_destroy (ra_file_t *file)
+{
+	ra_conf_t *conf = NULL;
+	ra_page_t *trav = NULL;
+
+	conf = file->conf;
+
+	ra_conf_lock (conf);
+	{
+		file->prev->next = file->next;
+		file->next->prev = file->prev;
+	}
+	ra_conf_unlock (conf);
+
+	trav = file->pages.next;
+	while (trav != &file->pages) {
+		ra_page_error (trav, -1, EINVAL);
+		trav = file->pages.next;
+	}
+
+	pthread_mutex_destroy (&file->file_lock);
+	free (file);
+}
+
diff --git a/xlators/performance/read-ahead/src/read-ahead.c b/xlators/performance/read-ahead/src/read-ahead.c
new file mode 100644
index 00000000000..0060e00fd41
--- /dev/null
+++ b/xlators/performance/read-ahead/src/read-ahead.c
@@ -0,0 +1,890 @@
+/*
+  Copyright (c) 2006, 2007, 2008, 2009 Z RESEARCH, Inc. <http://www.zresearch.com>
+  This file is part of GlusterFS.
+
+  GlusterFS is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published
+  by the Free Software Foundation; either version 3 of the License,
+  or (at your option) any later version.
+
+  GlusterFS is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see
+  <http://www.gnu.org/licenses/>.
+*/
+
+/* 
+   TODO:
+   - handle O_DIRECT
+   - maintain offset, flush on lseek
+   - ensure efficient memory managment in case of random seek
+*/
+
+#ifndef _CONFIG_H
+#define _CONFIG_H
+#include "config.h"
+#endif
+
+#include "glusterfs.h"
+#include "logging.h"
+#include "dict.h"
+#include "xlator.h"
+#include "read-ahead.h"
+#include <assert.h>
+#include <sys/time.h>
+
+
+static void
+read_ahead (call_frame_t *frame,
+            ra_file_t *file);
+
+
+int
+ra_open_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+             int32_t op_ret, int32_t op_errno, fd_t *fd)
+{
+	ra_conf_t  *conf = NULL;
+	ra_file_t  *file = NULL;
+	int         ret = 0;
+
+	conf  = this->private;
+
+	if (op_ret == -1) {
+		goto unwind;
+	}
+
+	file = CALLOC (1, sizeof (*file));
+	if (!file) {
+		gf_log (this->name, GF_LOG_ERROR,
+			"out of memory :(");
+		goto unwind;
+	}
+
+	ret = fd_ctx_set (fd, this, (uint64_t)(long)file);
+
+	/* If mandatory locking has been enabled on this file,
+	   we disable caching on it */
+
+	if ((fd->inode->st_mode & S_ISGID) && !(fd->inode->st_mode & S_IXGRP))
+		file->disabled = 1;
+
+	/* If O_DIRECT open, we disable caching on it */
+
+	if ((fd->flags & O_DIRECT) || (fd->flags & O_WRONLY))
+		file->disabled = 1;
+
+	file->offset = (unsigned long long) 0;
+	file->conf = conf;
+	file->pages.next = &file->pages;
+	file->pages.prev = &file->pages;
+	file->pages.offset = (unsigned long long) 0;
+	file->pages.file = file;
+
+	ra_conf_lock (conf);
+	{
+		file->next = conf->files.next;
+		conf->files.next = file;
+		file->next->prev = file;
+		file->prev = &conf->files;
+	}
+	ra_conf_unlock (conf);
+
+	file->fd = fd;
+	file->page_count = conf->page_count;
+	file->page_size = conf->page_size;
+	pthread_mutex_init (&file->file_lock, NULL);
+
+	if (!file->disabled) {
+		file->page_count = 1;
+	}
+
+unwind:
+	STACK_UNWIND (frame, op_ret, op_errno, fd);
+
+	return 0;
+}
+
+
+int
+ra_create_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+               int32_t op_ret, int32_t op_errno,
+	       fd_t *fd, inode_t *inode, struct stat *buf)
+{
+	ra_conf_t  *conf = NULL;
+	ra_file_t  *file = NULL;
+	int         ret = 0;
+
+	conf  = this->private;
+
+	if (op_ret == -1) {
+		goto unwind;
+	}
+
+	file = CALLOC (1, sizeof (*file));
+	if (!file) {
+		gf_log (this->name, GF_LOG_ERROR,
+			"out of memory :(");
+		goto unwind;
+	}
+
+	ret = fd_ctx_set (fd, this, (uint64_t)(long)file);
+
+	/* If mandatory locking has been enabled on this file,
+	   we disable caching on it */
+
+	if ((fd->inode->st_mode & S_ISGID) && !(fd->inode->st_mode & S_IXGRP))
+		file->disabled = 1;
+
+	/* If O_DIRECT open, we disable caching on it */
+
+	if ((fd->flags & O_DIRECT) || (fd->flags & O_WRONLY))
+			file->disabled = 1;
+
+	file->offset = (unsigned long long) 0;
+	//file->size = fd->inode->buf.st_size;
+	file->conf = conf;
+	file->pages.next = &file->pages;
+	file->pages.prev = &file->pages;
+	file->pages.offset = (unsigned long long) 0;
+	file->pages.file = file;
+
+	ra_conf_lock (conf);
+	{
+		file->next = conf->files.next;
+		conf->files.next = file;
+		file->next->prev = file;
+		file->prev = &conf->files;
+	}
+	ra_conf_unlock (conf);
+
+	file->fd = fd;
+	file->page_count = conf->page_count;
+	file->page_size = conf->page_size;
+	pthread_mutex_init (&file->file_lock, NULL);
+
+unwind:
+	STACK_UNWIND (frame, op_ret, op_errno, fd, inode, buf);
+
+	return 0;
+}
+
+
+int
+ra_open (call_frame_t *frame, xlator_t *this,
+         loc_t *loc, int32_t flags, fd_t *fd)
+{
+	STACK_WIND (frame, ra_open_cbk,
+		    FIRST_CHILD (this),
+		    FIRST_CHILD (this)->fops->open,
+		    loc, flags, fd);
+
+	return 0;
+}
+
+int
+ra_create (call_frame_t *frame, xlator_t *this,
+	   loc_t *loc, int32_t flags, mode_t mode, fd_t *fd)
+{
+	STACK_WIND (frame, ra_create_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->create,
+		    loc, flags, mode, fd);
+
+	return 0;
+}
+
+/* free cache pages between offset and offset+size,
+   does not touch pages with frames waiting on it
+*/
+
+static void
+flush_region (call_frame_t *frame,
+              ra_file_t *file,
+              off_t offset,
+              off_t size)
+{
+	ra_page_t *trav = NULL;
+	ra_page_t *next = NULL;
+
+
+	ra_file_lock (file);
+	{
+		trav = file->pages.next;
+		while (trav != &file->pages
+		       && trav->offset < (offset + size)) {
+
+			next = trav->next;
+			if (trav->offset >= offset && !trav->waitq) {
+				ra_page_purge (trav);
+			}
+			trav = next;
+		}
+	}
+	ra_file_unlock (file);
+}
+
+
+
+int
+ra_release (xlator_t *this,
+	    fd_t *fd)
+{
+	uint64_t tmp_file = 0;
+	int      ret = 0;
+
+	ret = fd_ctx_del (fd, this, &tmp_file);
+	
+	if (!ret) {
+		ra_file_destroy ((ra_file_t *)(long)tmp_file);
+	}
+
+	return 0;
+}
+
+
+void
+read_ahead (call_frame_t *frame, ra_file_t *file)
+{
+	off_t      ra_offset = 0;
+	size_t     ra_size = 0;
+	off_t      trav_offset = 0;
+	ra_page_t *trav = NULL;
+	off_t      cap = 0;
+	char       fault = 0;
+
+	if (!file->page_count)
+		return;
+
+	ra_size   = file->page_size * file->page_count;
+	ra_offset = floor (file->offset, file->page_size);
+	cap       = file->size ? file->size : file->offset + ra_size;
+
+	while (ra_offset < min (file->offset + ra_size, cap)) {
+
+		ra_file_lock (file);
+		{
+			trav = ra_page_get (file, ra_offset);
+		}
+		ra_file_unlock (file);
+
+		if (!trav)
+			break;
+
+		ra_offset += file->page_size;
+	}
+
+	if (trav)
+		/* comfortable enough */
+		return;
+
+	trav_offset = ra_offset;
+
+	trav = file->pages.next;
+	cap  = file->size ? file->size : ra_offset + ra_size;
+
+	while (trav_offset < min(ra_offset + ra_size, cap)) {
+		fault = 0;
+		ra_file_lock (file);
+		{
+			trav = ra_page_get (file, trav_offset);
+			if (!trav) {
+				fault = 1;
+				trav = ra_page_create (file, trav_offset);
+				if (trav) 
+					trav->dirty = 1;
+			}
+		}
+		ra_file_unlock (file);
+
+		if (!trav) {
+			/* OUT OF MEMORY */
+			break;
+		}
+
+		if (fault) {
+			gf_log (frame->this->name, GF_LOG_DEBUG,
+				"RA at offset=%"PRId64, trav_offset);
+			ra_page_fault (file, frame, trav_offset);
+		}
+		trav_offset += file->page_size;
+	}
+
+	return;
+}
+
+
+int
+ra_need_atime_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                   int32_t op_ret, int32_t op_errno, struct iovec *vector,
+                   int32_t count, struct stat *stbuf)
+{
+	STACK_DESTROY (frame->root);
+	return 0;
+}
+
+
+static void
+dispatch_requests (call_frame_t *frame,
+                   ra_file_t *file)
+{
+	ra_local_t   *local = NULL;
+	ra_conf_t    *conf = NULL;
+	off_t         rounded_offset = 0;
+	off_t         rounded_end = 0;
+	off_t         trav_offset = 0;
+	ra_page_t    *trav = NULL;
+	call_frame_t *ra_frame = NULL;
+	char          need_atime_update = 1;
+	char          fault = 0;
+
+
+	local = frame->local;
+	conf  = file->conf;
+
+	rounded_offset = floor (local->offset, file->page_size);
+	rounded_end    = roof (local->offset + local->size, file->page_size);
+
+	trav_offset = rounded_offset;
+	trav        = file->pages.next;
+
+	while (trav_offset < rounded_end) {
+		fault = 0;
+
+		ra_file_lock (file);
+		{
+			trav = ra_page_get (file, trav_offset);
+			if (!trav) {
+				trav = ra_page_create (file, trav_offset);
+				fault = 1;
+				need_atime_update = 0;
+			}
+
+			if (!trav)
+				goto unlock;
+
+			if (trav->ready) {
+				gf_log (frame->this->name, GF_LOG_DEBUG,
+					"HIT at offset=%"PRId64".",
+					trav_offset);
+				ra_frame_fill (trav, frame);
+			} else {
+				gf_log (frame->this->name, GF_LOG_DEBUG,
+					"IN-TRANSIT at offset=%"PRId64".",
+					trav_offset);
+				ra_wait_on_page (trav, frame);
+				need_atime_update = 0;
+			}
+		}
+	unlock:
+		ra_file_unlock (file);
+
+		if (fault) {
+			gf_log (frame->this->name, GF_LOG_DEBUG,
+				"MISS at offset=%"PRId64".",
+				trav_offset);
+			ra_page_fault (file, frame, trav_offset);
+		}
+
+		trav_offset += file->page_size;
+	}
+
+	if (need_atime_update && conf->force_atime_update) {
+		/* TODO: use untimens() since readv() can confuse underlying
+		   io-cache and others */
+		ra_frame = copy_frame (frame);
+		STACK_WIND (ra_frame, ra_need_atime_cbk,
+			    FIRST_CHILD (frame->this), 
+			    FIRST_CHILD (frame->this)->fops->readv,
+			    file->fd, 1, 1);
+	}
+
+	return ;
+}
+
+
+int
+ra_readv_disabled_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                       int32_t op_ret, int32_t op_errno,
+		       struct iovec *vector, int32_t count, struct stat *stbuf)
+{
+	STACK_UNWIND (frame, op_ret, op_errno, vector, count, stbuf);
+
+	return 0;
+}
+
+
+int
+ra_readv (call_frame_t *frame, xlator_t *this,
+	  fd_t *fd, size_t size, off_t offset)
+{
+	ra_file_t    *file = NULL;
+	ra_local_t   *local = NULL;
+	ra_conf_t    *conf = NULL;
+	int           op_errno = 0;
+	int           ret = 0;
+	char expected_offset = 1;
+	uint64_t tmp_file = 0;
+
+	conf = this->private;
+
+	gf_log (this->name, GF_LOG_DEBUG,
+		"NEW REQ at offset=%"PRId64" for size=%"GF_PRI_SIZET"",
+		offset, size);
+
+	ret = fd_ctx_get (fd, this, &tmp_file);
+	file = (ra_file_t *)(long)tmp_file;
+
+	if (file->offset != offset) {
+		gf_log (this->name, GF_LOG_DEBUG,
+			"unexpected offset (%"PRId64" != %"PRId64") resetting",
+			file->offset, offset);
+
+		expected_offset = file->expected = file->page_count = 0;
+	} else {
+		gf_log (this->name, GF_LOG_DEBUG,
+			"expected offset (%"PRId64") when page_count=%d",
+			offset, file->page_count);
+
+		if (file->expected < (conf->page_size * conf->page_count)) {
+			file->expected += size;
+			file->page_count = min ((file->expected / file->page_size),
+						conf->page_count);
+		}
+	}
+
+	if (!expected_offset) {
+		flush_region (frame, file, 0, file->pages.prev->offset + 1);
+	}
+
+	if (file->disabled) {
+		STACK_WIND (frame, ra_readv_disabled_cbk,
+			    FIRST_CHILD (frame->this), 
+			    FIRST_CHILD (frame->this)->fops->readv,
+			    file->fd, size, offset);
+		return 0;
+	}
+
+	local = (void *) CALLOC (1, sizeof (*local));
+	if (!local) {
+		gf_log (this->name, GF_LOG_ERROR,
+			"out of memory :(");
+		op_errno = ENOMEM;
+		goto unwind;
+	}
+
+	local->fd         = fd;
+	local->offset     = offset;
+	local->size       = size;
+	local->wait_count = 1;
+
+	local->fill.next  = &local->fill;
+	local->fill.prev  = &local->fill;
+
+	pthread_mutex_init (&local->local_lock, NULL);
+
+	frame->local = local;
+
+	dispatch_requests (frame, file);
+
+	flush_region (frame, file, 0, floor (offset, file->page_size));
+
+	read_ahead (frame, file);
+
+	ra_frame_return (frame);
+
+	file->offset = offset + size;
+
+	return 0;
+
+unwind:
+	STACK_UNWIND (frame, -1, op_errno, NULL, 0, NULL);
+
+	return 0;
+}
+
+
+int
+ra_flush_cbk (call_frame_t *frame,
+              void *cookie,
+              xlator_t *this,
+              int32_t op_ret,
+              int32_t op_errno)
+{
+	STACK_UNWIND (frame, op_ret, op_errno);
+	return 0;
+}
+
+
+int
+ra_flush (call_frame_t *frame, xlator_t *this, fd_t *fd)
+{
+	ra_file_t *file = NULL;
+	int        ret = 0;
+	uint64_t tmp_file = 0;
+
+	ret = fd_ctx_get (fd, this, &tmp_file);
+	file = (ra_file_t *)(long)tmp_file;
+
+	if (file) {
+		flush_region (frame, file, 0, file->pages.prev->offset+1);
+	}
+
+	STACK_WIND (frame, ra_flush_cbk,
+		    FIRST_CHILD (this),
+		    FIRST_CHILD (this)->fops->flush,
+		    fd);
+	return 0;
+}
+
+
+int
+ra_fsync (call_frame_t *frame, xlator_t *this, fd_t *fd,
+          int32_t datasync)
+{
+	ra_file_t *file = NULL;
+	int        ret = 0;
+	uint64_t tmp_file = 0;
+
+	ret = fd_ctx_get (fd, this, &tmp_file);
+	file = (ra_file_t *)(long)tmp_file;
+
+	if (file) {
+		flush_region (frame, file, 0, file->pages.prev->offset+1);
+	}
+
+	STACK_WIND (frame, ra_flush_cbk,
+		    FIRST_CHILD (this),
+		    FIRST_CHILD (this)->fops->fsync,
+		    fd, datasync);
+	return 0;
+}
+
+
+int
+ra_writev_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+               int32_t op_ret, int32_t op_errno, struct stat *stbuf)
+{
+	fd_t      *fd = NULL;
+	ra_file_t *file = NULL;
+	int        ret = 0;
+	uint64_t tmp_file = 0;
+
+	fd = frame->local;
+
+	ret = fd_ctx_get (fd, this, &tmp_file);
+	file = (ra_file_t *)(long)tmp_file;
+
+	if (file) {
+		flush_region (frame, file, 0, file->pages.prev->offset+1);
+	}
+
+	frame->local = NULL;
+	STACK_UNWIND (frame, op_ret, op_errno, stbuf);
+	return 0;
+}
+
+
+int
+ra_writev (call_frame_t *frame, xlator_t *this, fd_t *fd,
+           struct iovec *vector, int32_t count, off_t offset)
+{
+	ra_file_t *file = NULL;
+	int        ret = 0;
+	uint64_t tmp_file = 0;
+
+	ret = fd_ctx_get (fd, this, &tmp_file);
+	file = (ra_file_t *)(long)tmp_file;
+
+	if (file) {
+		flush_region (frame, file, 0, file->pages.prev->offset+1);
+
+		/* reset the read-ahead counters too */
+		file->expected = file->page_count = 0;
+	}
+
+	frame->local = fd;
+
+	STACK_WIND (frame, ra_writev_cbk,
+		    FIRST_CHILD(this),
+		    FIRST_CHILD(this)->fops->writev,
+		    fd, vector, count, offset);
+
+	return 0;
+}
+
+
+int
+ra_attr_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+	     int32_t op_ret, int32_t op_errno, struct stat *buf)
+{
+	STACK_UNWIND (frame, op_ret, op_errno, buf);
+	return 0;
+}
+
+
+int
+ra_truncate (call_frame_t *frame, xlator_t *this,
+             loc_t *loc, off_t offset)
+{
+	ra_file_t *file = NULL;
+	fd_t      *iter_fd = NULL;
+	inode_t   *inode = NULL;
+	int        ret = 0;
+	uint64_t tmp_file = 0;
+
+	inode = loc->inode;
+
+	LOCK (&inode->lock);
+	{
+		list_for_each_entry (iter_fd, &inode->fd_list, inode_list) {
+			ret = fd_ctx_get (iter_fd, this, &tmp_file);
+			file = (ra_file_t *)(long)tmp_file;
+
+			if (!file)
+				continue;
+			flush_region (frame, file, 0,
+				      file->pages.prev->offset + 1);
+		}
+	}
+	UNLOCK (&inode->lock);
+
+	STACK_WIND (frame, ra_attr_cbk,
+		    FIRST_CHILD (this),
+		    FIRST_CHILD (this)->fops->truncate,
+		    loc, offset);
+	return 0;
+}
+
+
+int
+ra_fstat (call_frame_t *frame, xlator_t *this,
+	  fd_t *fd)
+{
+	ra_file_t *file = NULL;
+	fd_t      *iter_fd = NULL;
+	inode_t   *inode = NULL;
+	int        ret = 0;
+	uint64_t tmp_file = 0;
+
+	inode = fd->inode;
+
+	LOCK (&inode->lock);
+	{
+		list_for_each_entry (iter_fd, &inode->fd_list, inode_list) {
+			ret = fd_ctx_get (iter_fd, this, &tmp_file);
+			file = (ra_file_t *)(long)tmp_file;
+
+			if (!file)
+				continue;
+			flush_region (frame, file, 0,
+				      file->pages.prev->offset + 1);
+		}
+	}
+	UNLOCK (&inode->lock);
+
+	STACK_WIND (frame, ra_attr_cbk,
+		    FIRST_CHILD (this),
+		    FIRST_CHILD (this)->fops->fstat,
+		    fd);
+	return 0;
+}
+
+
+int
+ra_fchown (call_frame_t *frame, xlator_t *this,
+	   fd_t *fd, uid_t uid, gid_t gid)
+{
+	ra_file_t *file = NULL;
+	fd_t      *iter_fd = NULL;
+	inode_t   *inode = NULL;
+	int        ret = 0;
+	uint64_t tmp_file = 0;
+
+	inode = fd->inode;
+
+	LOCK (&inode->lock);
+	{
+		list_for_each_entry (iter_fd, &inode->fd_list, inode_list) {
+			ret = fd_ctx_get (iter_fd, this, &tmp_file);
+			file = (ra_file_t *)(long)tmp_file;
+
+			if (!file)
+				continue;
+			flush_region (frame, file, 0,
+				      file->pages.prev->offset + 1);
+		}
+	}
+	UNLOCK (&inode->lock);
+
+	STACK_WIND (frame, ra_attr_cbk,
+		    FIRST_CHILD (this),
+		    FIRST_CHILD (this)->fops->fchown,
+		    fd, uid, gid);
+	return 0;
+}
+
+
+int
+ra_ftruncate (call_frame_t *frame, xlator_t *this,
+              fd_t *fd, off_t offset)
+{
+	ra_file_t *file = NULL;
+	fd_t      *iter_fd = NULL;
+	inode_t   *inode = NULL;
+	int        ret = 0;
+	uint64_t tmp_file = 0;
+
+	inode = fd->inode;
+
+	LOCK (&inode->lock);
+	{
+		list_for_each_entry (iter_fd, &inode->fd_list, inode_list) {
+			ret = fd_ctx_get (iter_fd, this, &tmp_file);
+			file = (ra_file_t *)(long)tmp_file;
+			if (!file)
+				continue;
+			flush_region (frame, file, 0,
+				      file->pages.prev->offset + 1);
+		}
+	}
+	UNLOCK (&inode->lock);
+
+	STACK_WIND (frame, ra_attr_cbk,
+		    FIRST_CHILD (this),
+		    FIRST_CHILD (this)->fops->ftruncate,
+		    fd, offset);
+	return 0;
+}
+
+
+int
+init (xlator_t *this)
+{
+	ra_conf_t *conf;
+	dict_t *options = this->options;
+	char *page_size_string = NULL;
+	char *page_count_string = NULL;
+
+	if (!this->children || this->children->next) {
+		gf_log (this->name,  GF_LOG_ERROR,
+			"FATAL: read-ahead not configured with exactly one child");
+		return -1;
+	}
+
+	if (!this->parents) {
+		gf_log (this->name, GF_LOG_WARNING,
+			"dangling volume. check volfile ");
+	}
+ 
+	conf = (void *) CALLOC (1, sizeof (*conf));
+	ERR_ABORT (conf);
+	conf->page_size = 256 * 1024;
+	conf->page_count = 2;
+
+	if (dict_get (options, "page-size"))
+		page_size_string = data_to_str (dict_get (options,
+							  "page-size"));
+	if (page_size_string)
+	{
+		if (gf_string2bytesize (page_size_string, &conf->page_size) != 0)
+		{
+			gf_log ("read-ahead", 
+				GF_LOG_ERROR, 
+				"invalid number format \"%s\" of \"option page-size\"", 
+				page_size_string);
+			return -1;
+		}
+      
+		gf_log (this->name, GF_LOG_DEBUG, "Using conf->page_size = %"PRIu64"",
+			conf->page_size);
+	}
+  
+	if (dict_get (options, "page-count"))
+		page_count_string = data_to_str (dict_get (options, 
+							   "page-count"));
+	if (page_count_string)
+	{
+		if (gf_string2uint_base10 (page_count_string, &conf->page_count) != 0)
+		{
+			gf_log ("read-ahead", 
+				GF_LOG_ERROR, 
+				"invalid number format \"%s\" of \"option page-count\"", 
+				page_count_string);
+			return -1;
+		}
+		gf_log (this->name, GF_LOG_DEBUG, "Using conf->page_count = %u",
+			conf->page_count);
+	}
+  
+	if (dict_get (options, "force-atime-update")) {
+		char *force_atime_update_str = data_to_str (dict_get (options,
+								      "force-atime-update"));
+		if (gf_string2boolean (force_atime_update_str, &conf->force_atime_update) == -1) {
+			gf_log (this->name, GF_LOG_ERROR,
+				"'force-atime-update' takes only boolean options");
+			return -1;
+		}
+		if (conf->force_atime_update)
+			gf_log (this->name, GF_LOG_DEBUG, "Forcing atime updates on cache hit");
+	}
+
+	conf->files.next = &conf->files;
+	conf->files.prev = &conf->files;
+
+	pthread_mutex_init (&conf->conf_lock, NULL);
+	this->private = conf;
+	return 0;
+}
+
+void
+fini (xlator_t *this)
+{
+	ra_conf_t *conf = this->private;
+
+	pthread_mutex_destroy (&conf->conf_lock);
+	FREE (conf);
+
+	this->private = NULL;
+	return;
+}
+
+struct xlator_fops fops = {
+	.open        = ra_open,
+	.create      = ra_create,
+	.readv       = ra_readv,
+	.writev      = ra_writev,
+	.flush       = ra_flush,
+	.fsync       = ra_fsync,
+	.truncate    = ra_truncate,
+	.ftruncate   = ra_ftruncate,
+	.fstat       = ra_fstat,
+	.fchown      = ra_fchown,
+};
+
+struct xlator_mops mops = {
+};
+
+struct xlator_cbks cbks = {
+	.release       = ra_release,
+};
+
+struct volume_options options[] = {
+	{ .key  = {"force-atime-update"}, 
+	  .type = GF_OPTION_TYPE_BOOL 
+	},
+	{ .key  = {"page-size"}, 
+	  .type = GF_OPTION_TYPE_SIZET, 
+	  .min  = 64 * GF_UNIT_KB, 
+	  .max  = 2 * GF_UNIT_MB 
+	},
+	{ .key  = {"page-count"}, 
+	  .type = GF_OPTION_TYPE_INT, 
+	  .min  = 1, 
+	  .max  = 16 
+	},
+	{ .key = {NULL} },
+};
diff --git a/xlators/performance/read-ahead/src/read-ahead.h b/xlators/performance/read-ahead/src/read-ahead.h
new file mode 100644
index 00000000000..d624ca8abc8
--- /dev/null
+++ b/xlators/performance/read-ahead/src/read-ahead.h
@@ -0,0 +1,194 @@
+/*
+  Copyright (c) 2006, 2007, 2008 Z RESEARCH, Inc. <http://www.zresearch.com>
+  This file is part of GlusterFS.
+
+  GlusterFS is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published
+  by the Free Software Foundation; either version 3 of the License,
+  or (at your option) any later version.
+
+  GlusterFS is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see
+  <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __READ_AHEAD_H
+#define __READ_AHEAD_H
+
+#ifndef _CONFIG_H
+#define _CONFIG_H
+#include "config.h"
+#endif
+
+
+#include "glusterfs.h"
+#include "logging.h"
+#include "dict.h"
+#include "xlator.h"
+#include "common-utils.h"
+
+struct ra_conf;
+struct ra_local;
+struct ra_page;
+struct ra_file;
+struct ra_waitq;
+
+
+struct ra_waitq {
+	struct ra_waitq *next;
+	void            *data;
+};
+
+
+struct ra_fill {
+	struct ra_fill *next;
+	struct ra_fill *prev;
+	off_t           offset;
+	size_t          size;
+	struct iovec   *vector;
+	int32_t         count;
+	dict_t         *refs;
+};
+
+
+struct ra_local {
+	mode_t            mode;
+	struct ra_fill    fill;
+	off_t             offset;
+	size_t            size;
+	int32_t           op_ret;
+	int32_t           op_errno;
+	off_t             pending_offset;
+	size_t            pending_size;
+	fd_t             *fd;
+	int32_t           wait_count;
+	pthread_mutex_t   local_lock;
+};
+
+
+struct ra_page {
+	struct ra_page   *next;
+	struct ra_page   *prev;
+	struct ra_file   *file;
+	char              dirty;
+	char              ready;
+	struct iovec     *vector;
+	int32_t           count;
+	off_t             offset;
+	size_t            size;
+	struct ra_waitq  *waitq;
+	dict_t           *ref;
+};
+
+
+struct ra_file {
+	struct ra_file    *next;
+	struct ra_file    *prev;
+	struct ra_conf    *conf;
+	fd_t              *fd;
+	int                disabled;
+	size_t             expected;
+	struct ra_page     pages;
+	off_t              offset;
+	size_t             size;
+	int32_t            refcount;
+	pthread_mutex_t    file_lock;
+	struct stat        stbuf;
+	uint64_t           page_size;
+	uint32_t           page_count;
+};
+
+
+struct ra_conf {
+	uint64_t          page_size;
+	uint32_t          page_count;
+	void             *cache_block;
+	struct ra_file    files;
+	gf_boolean_t      force_atime_update;
+	pthread_mutex_t   conf_lock;
+};
+
+
+typedef struct ra_conf ra_conf_t;
+typedef struct ra_local ra_local_t;
+typedef struct ra_page ra_page_t;
+typedef struct ra_file ra_file_t;
+typedef struct ra_waitq ra_waitq_t;
+typedef struct ra_fill ra_fill_t;
+
+ra_page_t *
+ra_page_get (ra_file_t *file,
+	     off_t offset);
+ra_page_t *
+ra_page_create (ra_file_t *file,
+		off_t offset);
+void
+ra_page_fault (ra_file_t *file,
+	       call_frame_t *frame,
+	       off_t offset);
+void
+ra_wait_on_page (ra_page_t *page,
+		 call_frame_t *frame);
+ra_waitq_t *
+ra_page_wakeup (ra_page_t *page);
+
+void
+ra_page_flush (ra_page_t *page);
+
+ra_waitq_t *
+ra_page_error (ra_page_t *page,
+	       int32_t op_ret,
+	       int32_t op_errno);
+void
+ra_page_purge (ra_page_t *page);
+
+void
+ra_frame_return (call_frame_t *frame);
+void
+ra_frame_fill (ra_page_t *page,
+	       call_frame_t *frame);
+
+void
+ra_file_destroy (ra_file_t *file);
+
+static inline void
+ra_file_lock (ra_file_t *file)
+{
+	pthread_mutex_lock (&file->file_lock);
+}
+
+static inline void
+ra_file_unlock (ra_file_t *file)
+{
+	pthread_mutex_unlock (&file->file_lock);
+}
+
+static inline void
+ra_conf_lock (ra_conf_t *conf)
+{
+	pthread_mutex_lock (&conf->conf_lock);
+}
+
+static inline void
+ra_conf_unlock (ra_conf_t *conf)
+{
+	pthread_mutex_unlock (&conf->conf_lock);
+}
+static inline void
+ra_local_lock (ra_local_t *local)
+{
+	pthread_mutex_lock (&local->local_lock);
+}
+
+static inline void
+ra_local_unlock (ra_local_t *local)
+{
+	pthread_mutex_unlock (&local->local_lock);
+}
+
+#endif /* __READ_AHEAD_H */
diff --git a/xlators/performance/stat-prefetch/Makefile.am b/xlators/performance/stat-prefetch/Makefile.am
new file mode 100644
index 00000000000..af437a64d6d
--- /dev/null
+++ b/xlators/performance/stat-prefetch/Makefile.am
@@ -0,0 +1 @@
+SUBDIRS = src
diff --git a/xlators/performance/stat-prefetch/src/Makefile.am b/xlators/performance/stat-prefetch/src/Makefile.am
new file mode 100644
index 00000000000..e52f2df48fd
--- /dev/null
+++ b/xlators/performance/stat-prefetch/src/Makefile.am
@@ -0,0 +1,11 @@
+xlator_PROGRAMS = stat-prefetch.so
+xlatordir = $(libdir)/glusterfs/$(PACKAGE_VERSION)/xlator/performance
+
+stat_prefetch_so_SOURCES = stat-prefetch.c
+noinst_HEADERS = stat-prefetch.h
+
+AM_CFLAGS = -fPIC -D_FILE_OFFSET_BITS=64 -D_GNU_SOURCE -Wall \
+	-I$(top_srcdir)/libglusterfs/src -shared -nostartfiles
+
+CLEANFILES = 
+
diff --git a/xlators/performance/stat-prefetch/src/stat-prefetch.c b/xlators/performance/stat-prefetch/src/stat-prefetch.c
new file mode 100644
index 00000000000..f2a78f676f9
--- /dev/null
+++ b/xlators/performance/stat-prefetch/src/stat-prefetch.c
@@ -0,0 +1,508 @@
+/*
+   Copyright (c) 2006, 2007, 2008 Z RESEARCH, Inc. <http://www.zresearch.com>
+   This file is part of GlusterFS.
+
+   GlusterFS is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published
+   by the Free Software Foundation; either version 3 of the License,
+   or (at your option) any later version.
+
+   GlusterFS is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see
+   <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef _CONFIG_H
+#define _CONFIG_H
+#include "config.h"
+#endif
+
+#include "glusterfs.h"
+#include "stat-prefetch.h"
+#include "dict.h"
+#include "xlator.h"
+#include <sys/time.h>
+
+struct sp_cache {
+  struct sp_cache *next;
+  struct sp_cache *prev;
+  pid_t pid;
+  long long tv_time;
+  char *dirname;
+  dir_entry_t entries;
+  int32_t count;
+  pthread_mutex_t lock;
+};
+
+static void
+stat_prefetch_cache_flush (struct sp_cache *cache, int32_t force)
+{
+  struct sp_cache *trav;
+  struct timeval tv;
+  long long tv_time;
+
+  gettimeofday (&tv, NULL);
+  tv_time = (tv.tv_usec + (tv.tv_sec * 1000000));
+
+  pthread_mutex_lock (&cache->lock);
+
+  trav = cache->next;
+  while (trav != cache) {
+    struct sp_cache *next = trav->next;
+    {
+      if (tv_time > trav->tv_time || force) {
+	gf_log ("stat-prefetch",
+		GF_LOG_DEBUG,
+		"flush on: %s",
+		trav->dirname);
+	dir_entry_t *entries;
+
+	trav->prev->next = trav->next;
+	trav->next->prev = trav->prev;
+
+	entries = trav->entries.next;
+
+	while (entries) {
+	  dir_entry_t *nextentry = entries->next;
+	  {
+	    free (entries->name);
+	    free (entries);
+	  }
+	  entries = nextentry;
+	}
+	free (trav->dirname);
+	free (trav);
+      }
+    }
+    trav = next;
+  }
+
+  pthread_mutex_unlock (&cache->lock);
+}
+
+static int32_t
+stat_prefetch_cache_fill (struct sp_cache *cache,
+			  pid_t pid,
+			  char *dirname,
+			  dir_entry_t *entries)
+{
+  struct sp_cache *trav;
+  struct timeval tv;
+
+  pthread_mutex_unlock (&cache->lock);
+  trav = cache->next;
+  while (trav != cache) {
+    //    if (trav->pid == pid && !strcmp (trav->dirname, dirname)) {
+    if (!strcmp (trav->dirname, dirname)) {
+      break;
+    }
+    trav = trav->next;
+  }
+
+  if (trav == cache) {
+    trav = CALLOC (1, sizeof (*trav));
+    ERR_ABORT (trav);
+    trav->pid = pid;
+    trav->dirname = dirname;
+
+    trav->prev = cache->prev;
+    trav->next = cache;
+    trav->next->prev = trav;
+    trav->prev->next = trav;
+  } else {
+    free (dirname);
+  }
+
+  while (trav->entries.next) {
+    dir_entry_t *tmp = trav->entries.next;
+
+    trav->entries.next = trav->entries.next->next;
+    free (tmp->name);
+    free (tmp);
+  }
+  trav->entries.next = entries->next;
+  entries->next = NULL;
+
+  gettimeofday (&tv, NULL);
+  trav->tv_time = (tv.tv_usec + (tv.tv_sec * 1000000)) + cache->tv_time;
+
+  pthread_mutex_unlock (&cache->lock);
+  return 0;
+}
+
+static int32_t
+stat_prefetch_cache_lookup (struct sp_cache *cache,
+			    pid_t pid,
+			    const char *path,
+			    struct stat *buf)
+{
+  struct sp_cache *trav;
+  char *dirname = strdup (path);
+  char *filename = strrchr (dirname, '/');
+  dir_entry_t *entries;
+  dir_entry_t *prev = NULL;
+
+  *filename = '\0';
+  filename ++;
+
+  pthread_mutex_lock (&cache->lock);
+  trav = cache->next;
+  while (trav != cache) {
+    //    if ((trav->pid == pid) && !strcmp (dirname, trav->dirname))
+    if (!strcmp (dirname, trav->dirname))
+      break;
+    trav = trav->next;
+  }
+  if (trav == cache) {
+    free (dirname);
+    pthread_mutex_unlock (&cache->lock);
+    return -1;
+  }
+
+  entries = trav->entries.next;
+  prev = &trav->entries;
+  while (entries) {
+    if (!strcmp (entries->name, filename))
+      break;
+    prev = entries;
+    entries = entries->next;
+  }
+  if (!entries) {
+    free (dirname);
+    pthread_mutex_unlock (&cache->lock);
+    return -1;
+  }
+
+  *buf = entries->buf;
+  prev->next = entries->next;
+  free (entries->name);
+  free (entries);
+  free (dirname);
+
+  pthread_mutex_unlock (&cache->lock);
+
+  return 0;
+}
+
+			    
+int32_t
+stat_prefetch_readdir_cbk (call_frame_t *frame,
+			   void *cookie,
+			   xlator_t *this,
+			   int32_t op_ret,
+			   int32_t op_errno,
+			   dir_entry_t *entries,
+			   int32_t count)
+{
+  char *path = frame->local;
+  pid_t pid = frame->root->pid;
+  frame->local = NULL;
+
+  STACK_UNWIND (frame, op_ret, op_errno, entries, count);
+
+  if (op_ret == 0)
+    stat_prefetch_cache_fill (this->private,
+			      pid,
+			      path,
+			      entries);
+  else
+    free (path);
+
+  return 0;
+}
+
+int32_t
+stat_prefetch_readdir (call_frame_t *frame,
+		       xlator_t *this,
+		       const char *path)
+{
+  stat_prefetch_cache_flush (this->private, 0);
+
+  frame->local = strdup (path);
+  STACK_WIND (frame,
+	      stat_prefetch_readdir_cbk,
+	      FIRST_CHILD(this),
+	      FIRST_CHILD(this)->fops->readdir,
+	      path);
+  return 0;
+}
+
+
+int32_t
+stat_prefetch_getattr_cbk (call_frame_t *frame,
+			   void *cookie,
+			   xlator_t *this,
+			   int32_t op_ret,
+			   int32_t op_errno,
+			   struct stat *buf)
+{
+  STACK_UNWIND (frame, op_ret, op_errno, buf);
+  return 0;
+}
+
+int32_t
+stat_prefetch_getattr (call_frame_t *frame,
+		       struct xlator *this,
+		       const char *path)
+{
+  struct stat buf;
+  pid_t pid = frame->root->pid;
+  stat_prefetch_cache_flush (this->private, 0);
+
+  if (stat_prefetch_cache_lookup (this->private,
+				  pid,
+				  path,
+				  &buf) == 0) {
+    STACK_UNWIND (frame, 0, 0, &buf);
+    return 0;
+  }
+
+  STACK_WIND (frame,
+	      stat_prefetch_getattr_cbk,
+	      FIRST_CHILD(this),
+	      FIRST_CHILD(this)->fops->getattr,
+	      path);
+
+  return 0;
+}
+
+
+int32_t
+stat_prefetch_unlink_cbk (call_frame_t *frame,
+                          void *cookie,
+                          xlator_t *this,
+                          int32_t op_ret,
+                          int32_t op_errno)
+{
+  STACK_UNWIND (frame, op_ret, op_errno);
+  return 0;
+}
+
+int32_t
+stat_prefetch_unlink (call_frame_t *frame,
+                      struct xlator *this,
+                      const char *path)
+{
+  stat_prefetch_cache_flush (this->private, 1);
+
+  STACK_WIND (frame,
+              stat_prefetch_unlink_cbk,
+              FIRST_CHILD(this),
+              FIRST_CHILD(this)->fops->unlink,
+              path);
+
+  return 0;
+}
+
+
+int32_t
+stat_prefetch_chmod_cbk (call_frame_t *frame,
+			 void *cookie,
+			 xlator_t *this,
+			 int32_t op_ret,
+			 int32_t op_errno,
+			 struct stat *buf)
+{
+  STACK_UNWIND (frame, op_ret, op_errno, buf);
+  return 0;
+}
+
+int32_t
+stat_prefetch_chmod (call_frame_t *frame,
+		     struct xlator *this,
+		     const char *path,
+		     mode_t mode)
+{
+  stat_prefetch_cache_flush (this->private, 1);
+
+  STACK_WIND (frame,
+              stat_prefetch_chmod_cbk,
+              FIRST_CHILD(this),
+              FIRST_CHILD(this)->fops->chmod,
+              path,
+	      mode);
+
+  return 0;
+}
+
+
+int32_t
+stat_prefetch_chown_cbk (call_frame_t *frame,
+			 void *cookie,
+			 xlator_t *this,
+			 int32_t op_ret,
+			 int32_t op_errno,
+			 struct stat *buf)
+{
+  STACK_UNWIND (frame, op_ret, op_errno, buf);
+  return 0;
+}
+
+int32_t
+stat_prefetch_chown (call_frame_t *frame,
+		     struct xlator *this,
+		     const char *path,
+		     uid_t uid,
+		     gid_t gid)
+{
+  stat_prefetch_cache_flush (this->private, 1);
+
+  STACK_WIND (frame,
+              stat_prefetch_chown_cbk,
+              FIRST_CHILD(this),
+              FIRST_CHILD(this)->fops->chown,
+              path,
+	      uid,
+	      gid);
+
+  return 0;
+}
+
+
+int32_t
+stat_prefetch_utimes_cbk (call_frame_t *frame,
+                          void *cookie,
+                          xlator_t *this,
+                          int32_t op_ret,
+                          int32_t op_errno,
+			  struct stat *buf)
+{
+  STACK_UNWIND (frame, op_ret, op_errno, buf);
+  return 0;
+}
+
+int32_t
+stat_prefetch_utimes (call_frame_t *frame,
+		      struct xlator *this,
+		      const char *path,
+		      struct timespec *tvp)
+{
+  stat_prefetch_cache_flush (this->private, 1);
+
+  STACK_WIND (frame,
+              stat_prefetch_utimes_cbk,
+              FIRST_CHILD(this),
+              FIRST_CHILD(this)->fops->utimes,
+              path,
+	      tvp);
+
+  return 0;
+}
+
+
+int32_t
+stat_prefetch_truncate_cbk (call_frame_t *frame,
+			    void *cookie,
+			    xlator_t *this,
+			    int32_t op_ret,
+			    int32_t op_errno,
+			    struct stat *buf)
+{
+  STACK_UNWIND (frame, op_ret, op_errno, buf);
+  return 0;
+}
+
+int32_t
+stat_prefetch_truncate (call_frame_t *frame,
+			struct xlator *this,
+			const char *path,
+			off_t offset)
+{
+  stat_prefetch_cache_flush (this->private, 1);
+
+  STACK_WIND (frame,
+              stat_prefetch_truncate_cbk,
+              FIRST_CHILD(this),
+              FIRST_CHILD(this)->fops->truncate,
+              path,
+	      offset);
+
+  return 0;
+}
+
+
+int32_t
+stat_prefetch_rename_cbk (call_frame_t *frame,
+                          void *cookie,
+                          xlator_t *this,
+                          int32_t op_ret,
+                          int32_t op_errno)
+{
+  STACK_UNWIND (frame, op_ret, op_errno);
+  return 0;
+}
+
+int32_t
+stat_prefetch_rename (call_frame_t *frame,
+                      struct xlator *this,
+                      const char *oldpath,
+		      const char *newpath)
+{
+  stat_prefetch_cache_flush (this->private, 1);
+
+  STACK_WIND (frame,
+              stat_prefetch_rename_cbk,
+              FIRST_CHILD(this),
+              FIRST_CHILD(this)->fops->rename,
+              oldpath,
+	      newpath);
+
+  return 0;
+}
+
+int32_t 
+init (struct xlator *this)
+{
+  struct sp_cache *cache;
+  dict_t *options = this->options;
+
+  if (!this->children || this->children->next) {
+    gf_log ("stat-prefetch",
+	    GF_LOG_ERROR,
+	    "FATAL: translator %s does not have exactly one child node",
+	    this->name);
+    return -1;
+  }
+
+  cache = (void *) CALLOC (1, sizeof (*cache));
+  ERR_ABORT (cache);
+  cache->next = cache->prev = cache;
+
+  cache->tv_time = 1 * 1000000;
+
+  if (dict_get (options, "cache-seconds")) {
+    cache->tv_time = (data_to_int64 (dict_get (options, "cache-seconds")) *
+		      1000000);
+  }
+
+  pthread_mutex_init (&cache->lock, NULL);
+
+  this->private = cache;
+  return 0;
+}
+
+void
+fini (struct xlator *this)
+{
+  return;
+}
+
+
+struct xlator_fops fops = {
+  .getattr     = stat_prefetch_getattr,
+  .readdir     = stat_prefetch_readdir,
+  .unlink      = stat_prefetch_unlink,
+  .chmod       = stat_prefetch_chmod,
+  .chown       = stat_prefetch_chown,
+  .rename      = stat_prefetch_rename,
+  .utimes      = stat_prefetch_utimes,
+  .truncate    = stat_prefetch_truncate,
+};
+
+struct xlator_mops mops = {
+};
diff --git a/xlators/performance/stat-prefetch/src/stat-prefetch.h b/xlators/performance/stat-prefetch/src/stat-prefetch.h
new file mode 100644
index 00000000000..7d9645a2a81
--- /dev/null
+++ b/xlators/performance/stat-prefetch/src/stat-prefetch.h
@@ -0,0 +1,32 @@
+/*
+   Copyright (c) 2006, 2007, 2008 Z RESEARCH, Inc. <http://www.zresearch.com>
+   This file is part of GlusterFS.
+
+   GlusterFS is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published
+   by the Free Software Foundation; either version 3 of the License,
+   or (at your option) any later version.
+
+   GlusterFS is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see
+   <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef _STAT_PREFETCH_H_
+#define _STAT_PREFETCH_H_
+
+#ifndef _CONFIG_H
+#define _CONFIG_H
+#include "config.h"
+#endif
+
+#include <stdio.h>
+#include <sys/time.h>
+#include "xlator.h"
+
+#endif /* _STAT_PREFETCH_H_ */
diff --git a/xlators/performance/symlink-cache/Makefile.am b/xlators/performance/symlink-cache/Makefile.am
new file mode 100644
index 00000000000..d471a3f9243
--- /dev/null
+++ b/xlators/performance/symlink-cache/Makefile.am
@@ -0,0 +1,3 @@
+SUBDIRS = src
+
+CLEANFILES = 
diff --git a/xlators/performance/symlink-cache/src/Makefile.am b/xlators/performance/symlink-cache/src/Makefile.am
new file mode 100644
index 00000000000..b8b257c186c
--- /dev/null
+++ b/xlators/performance/symlink-cache/src/Makefile.am
@@ -0,0 +1,12 @@
+xlator_LTLIBRARIES = symlink-cache.la
+xlatordir = $(libdir)/glusterfs/$(PACKAGE_VERSION)/xlator/performance
+
+symlink_cache_la_LDFLAGS = -module -avoidversion 
+
+symlink_cache_la_SOURCES = symlink-cache.c
+symlink_cache_la_LIBADD = $(top_builddir)/libglusterfs/src/libglusterfs.la
+
+AM_CFLAGS = -fPIC -D_FILE_OFFSET_BITS=64 -D_GNU_SOURCE -Wall -D$(GF_HOST_OS)\
+	-I$(top_srcdir)/libglusterfs/src -shared -nostartfiles $(GF_CFLAGS)
+
+CLEANFILES = 
diff --git a/xlators/performance/symlink-cache/src/symlink-cache.c b/xlators/performance/symlink-cache/src/symlink-cache.c
new file mode 100644
index 00000000000..fc207a6272e
--- /dev/null
+++ b/xlators/performance/symlink-cache/src/symlink-cache.c
@@ -0,0 +1,399 @@
+/*
+  Copyright (c) 2008 Z RESEARCH, Inc. <http://www.zresearch.com>
+  This file is part of GlusterFS.
+
+  GlusterFS is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published
+  by the Free Software Foundation; either version 3 of the License,
+  or (at your option) any later version.
+
+  GlusterFS is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see
+  <http://www.gnu.org/licenses/>.
+*/
+
+
+#ifndef _CONFIG_H
+#define _CONFIG_H
+#include "config.h"
+#endif
+
+#include "glusterfs.h"
+#include "logging.h"
+#include "dict.h"
+#include "xlator.h"
+#include "list.h"
+#include "compat.h"
+#include "compat-errno.h"
+#include "common-utils.h"
+
+struct symlink_cache {
+	time_t ctime;
+	char   *readlink;
+};
+
+
+static int
+symlink_inode_ctx_get (inode_t *inode, xlator_t *this, void **ctx)
+{
+	int ret = 0;
+	uint64_t tmp_ctx = 0;
+	ret = inode_ctx_get (inode, this, &tmp_ctx);
+	if (-1 == ret)
+		gf_log (this->name, GF_LOG_ERROR, "dict get failed");
+	else
+		*ctx = (void *)(long)tmp_ctx;
+
+	return 0;
+}
+
+
+static int
+symlink_inode_ctx_set (inode_t *inode, xlator_t *this, void *ctx)
+{
+	int ret = 0;
+	ret = inode_ctx_put (inode, this, (uint64_t)(long) ctx);
+	if (-1 == ret)
+		gf_log (this->name, GF_LOG_ERROR, "dict set failed");
+
+	return 0;
+}
+
+
+int
+sc_cache_update (xlator_t *this, inode_t *inode, const char *link)
+{
+	struct symlink_cache *sc = NULL;
+
+	symlink_inode_ctx_get (inode, this, VOID(&sc));
+	if (!sc)
+		return 0;
+
+	if (!sc->readlink) {
+		gf_log (this->name, GF_LOG_DEBUG,
+			"updating cache: %s", link);
+
+		sc->readlink = strdup (link);
+	} else {
+		gf_log (this->name, GF_LOG_DEBUG,
+			"not updating existing cache: %s with %s",
+			sc->readlink, link);
+	}
+
+	return 0;
+}
+
+
+int
+sc_cache_set (xlator_t *this, inode_t *inode, struct stat *buf,
+	      const char *link)
+{
+	struct symlink_cache *sc = NULL;
+	int                   ret = -1;
+	int                   need_set = 0;
+
+
+	symlink_inode_ctx_get (inode, this, VOID(&sc));
+	if (!sc) {
+		need_set = 1;
+		sc = CALLOC (1, sizeof (*sc));
+		if (!sc) {
+			gf_log (this->name, GF_LOG_ERROR,
+				"out of memory :(");
+			goto err;
+		}
+	}
+
+	if (sc->readlink) {
+		gf_log (this->name, GF_LOG_DEBUG,
+			"replacing old cache: %s with new cache: %s",
+			sc->readlink, link);
+		FREE (sc->readlink);
+		sc->readlink = NULL;
+	}
+
+	if (link) {
+		sc->readlink = strdup (link);
+		if (!sc->readlink) {
+			gf_log (this->name, GF_LOG_ERROR,
+				"out of memory :(");
+			goto err;
+		}
+	}
+
+	sc->ctime = buf->st_ctime;
+
+	gf_log (this->name, GF_LOG_DEBUG,
+		"setting symlink cache: %s", link);
+
+	if (need_set) {
+		ret = symlink_inode_ctx_set (inode, this, sc);
+
+		if (ret < 0) {
+			gf_log (this->name, GF_LOG_ERROR,
+				"could not set inode context (%s)",
+				strerror (-ret));
+			goto err;
+		}
+	}
+
+	return 0;
+err:
+
+	if (sc) {
+		if (sc->readlink)
+			FREE (sc->readlink);
+		sc->readlink = NULL;
+		FREE (sc);
+	}
+
+	return -1;
+}
+
+
+int
+sc_cache_flush (xlator_t *this, inode_t *inode)
+{
+	struct symlink_cache *sc = NULL;
+
+	symlink_inode_ctx_get (inode, this, VOID(&sc));
+	if (!sc)
+		return 0;
+
+	if (sc->readlink) {
+		gf_log (this->name, GF_LOG_DEBUG,
+			"flushing cache: %s", sc->readlink);
+
+		FREE (sc->readlink);
+		sc->readlink = NULL;
+	}
+
+	FREE (sc);
+
+	return 0;
+}
+
+
+int
+sc_cache_validate (xlator_t *this, inode_t *inode, struct stat *buf)
+{
+	struct symlink_cache *sc = NULL;
+	uint64_t tmp_sc = 0;
+
+	if (!S_ISLNK (buf->st_mode)) {
+		sc_cache_flush (this, inode);
+		return 0;
+	}
+
+	symlink_inode_ctx_get (inode, this, VOID(&sc));
+
+	if (!sc) {
+		sc_cache_set (this, inode, buf, NULL);
+		inode_ctx_get (inode, this, &tmp_sc);
+
+		if (!sc) {
+			gf_log (this->name, GF_LOG_ERROR,
+				"out of memory :(");
+			return 0;
+		}
+		sc = (struct symlink_cache *)(long)tmp_sc;
+	}
+
+	if (sc->ctime == buf->st_ctime)
+		return 0;
+
+	/* STALE */
+	if (sc->readlink) {
+		gf_log (this->name, GF_LOG_DEBUG,
+			"flushing cache: %s", sc->readlink);
+
+		FREE (sc->readlink);
+		sc->readlink = NULL;
+	}
+
+	sc->ctime = buf->st_ctime;
+
+	return 0;
+}
+
+
+
+int
+sc_cache_get (xlator_t *this, inode_t *inode, char **link)
+{
+	struct symlink_cache *sc = NULL;
+
+	symlink_inode_ctx_get (inode, this, VOID(&sc));
+
+	if (!sc)
+		return 0;
+
+	if (link && sc->readlink)
+		*link = strdup (sc->readlink);
+	return 0;
+}
+
+
+int
+sc_readlink_cbk (call_frame_t *frame, void *cookie,
+		 xlator_t *this, int op_ret, int op_errno,
+		 const char *link)
+{
+	if (op_ret > 0)
+		sc_cache_update (this, frame->local, link);
+
+	inode_unref (frame->local);
+	frame->local = NULL;
+
+        STACK_UNWIND (frame, op_ret, op_errno, link);
+        return 0;
+}
+
+
+int
+sc_readlink (call_frame_t *frame, xlator_t *this,
+	     loc_t *loc, size_t size)
+{
+	char *link = NULL;
+
+	sc_cache_get (this, loc->inode, &link);
+
+	if (link) {
+		/* cache hit */
+		gf_log (this->name, GF_LOG_DEBUG,
+			"cache hit %s -> %s",
+			loc->path, link);
+		STACK_UNWIND (frame, strlen (link) + 1, 0, link);
+		FREE (link);
+		return 0;
+	}
+
+	frame->local = inode_ref (loc->inode);
+
+        STACK_WIND (frame, sc_readlink_cbk,
+                    FIRST_CHILD(this),
+                    FIRST_CHILD(this)->fops->readlink,
+                    loc, size);
+
+	return 0;
+}
+
+
+int
+sc_symlink_cbk (call_frame_t *frame, void *cookie,
+		xlator_t *this, int op_ret, int op_errno,
+		inode_t *inode, struct stat *buf)
+{
+	if (op_ret == 0) {
+		if (frame->local) {
+			sc_cache_set (this, inode, buf, frame->local);
+		}
+	}
+
+        STACK_UNWIND (frame, op_ret, op_errno, inode, buf);
+        return 0;
+}
+
+
+int
+sc_symlink (call_frame_t *frame, xlator_t *this,
+	    const char *dst, loc_t *src)
+{
+	frame->local = strdup (dst);
+
+        STACK_WIND (frame, sc_symlink_cbk,
+                    FIRST_CHILD(this),
+                    FIRST_CHILD(this)->fops->symlink,
+                    dst, src);
+
+	return 0;
+}
+
+
+int
+sc_lookup_cbk (call_frame_t *frame, void *cookie,
+	       xlator_t *this, int op_ret, int op_errno,
+	       inode_t *inode, struct stat *buf, dict_t *xattr)
+{
+	if (op_ret == 0)
+		sc_cache_validate (this, inode, buf);
+	else
+		sc_cache_flush (this, inode);
+
+        STACK_UNWIND (frame, op_ret, op_errno, inode, buf, xattr);
+        return 0;
+}
+
+
+int
+sc_lookup (call_frame_t *frame, xlator_t *this,
+	   loc_t *loc, dict_t *xattr_req)
+{
+        STACK_WIND (frame, sc_lookup_cbk,
+                    FIRST_CHILD(this),
+                    FIRST_CHILD(this)->fops->lookup,
+                    loc, xattr_req);
+
+        return 0;
+}
+
+
+int
+sc_forget (xlator_t *this,
+	   inode_t *inode)
+{
+	sc_cache_flush (this, inode);
+
+        return 0;
+}
+
+
+int32_t 
+init (xlator_t *this)
+{
+	
+        if (!this->children || this->children->next)
+        {
+                gf_log (this->name, GF_LOG_ERROR,
+                        "FATAL: volume (%s) not configured with exactly one "
+			"child", this->name);
+                return -1;
+        }
+
+	if (!this->parents) {
+		gf_log (this->name, GF_LOG_WARNING,
+			"dangling volume. check volfile ");
+	}
+
+        return 0;
+}
+
+
+void
+fini (xlator_t *this)
+{
+        return;
+}
+
+
+struct xlator_fops fops = {
+	.lookup      = sc_lookup,
+	.symlink     = sc_symlink,
+	.readlink    = sc_readlink,
+};
+
+struct xlator_mops mops = {
+};
+
+struct xlator_cbks cbks = {
+        .forget  = sc_forget,
+};
+
+struct volume_options options[] = {
+	{ .key = {NULL} },
+};
diff --git a/xlators/performance/write-behind/Makefile.am b/xlators/performance/write-behind/Makefile.am
new file mode 100644
index 00000000000..d471a3f9243
--- /dev/null
+++ b/xlators/performance/write-behind/Makefile.am
@@ -0,0 +1,3 @@
+SUBDIRS = src
+
+CLEANFILES = 
diff --git a/xlators/performance/write-behind/src/Makefile.am b/xlators/performance/write-behind/src/Makefile.am
new file mode 100644
index 00000000000..f800abad50d
--- /dev/null
+++ b/xlators/performance/write-behind/src/Makefile.am
@@ -0,0 +1,12 @@
+xlator_LTLIBRARIES = write-behind.la
+xlatordir = $(libdir)/glusterfs/$(PACKAGE_VERSION)/xlator/performance
+
+write_behind_la_LDFLAGS = -module -avoidversion 
+
+write_behind_la_SOURCES = write-behind.c
+write_behind_la_LIBADD = $(top_builddir)/libglusterfs/src/libglusterfs.la
+
+AM_CFLAGS = -fPIC -D_FILE_OFFSET_BITS=64 -D_GNU_SOURCE -Wall -D$(GF_HOST_OS)\
+	-I$(top_srcdir)/libglusterfs/src -shared -nostartfiles $(GF_CFLAGS)
+
+CLEANFILES = 
diff --git a/xlators/performance/write-behind/src/write-behind.c b/xlators/performance/write-behind/src/write-behind.c
new file mode 100644
index 00000000000..04a447d49e9
--- /dev/null
+++ b/xlators/performance/write-behind/src/write-behind.c
@@ -0,0 +1,1444 @@
+/*
+  Copyright (c) 2006, 2007, 2008, 2009 Z RESEARCH, Inc. <http://www.zresearch.com>
+  This file is part of GlusterFS.
+
+  GlusterFS is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published
+  by the Free Software Foundation; either version 3 of the License,
+  or (at your option) any later version.
+
+  GlusterFS is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see
+  <http://www.gnu.org/licenses/>.
+*/
+
+/*TODO: check for non null wb_file_data before getting wb_file */
+
+
+#ifndef _CONFIG_H
+#define _CONFIG_H
+#include "config.h"
+#endif
+
+#include "glusterfs.h"
+#include "logging.h"
+#include "dict.h"
+#include "xlator.h"
+#include "list.h"
+#include "compat.h"
+#include "compat-errno.h"
+#include "common-utils.h"
+
+#define MAX_VECTOR_COUNT 8
+ 
+typedef struct list_head list_head_t;
+struct wb_conf;
+struct wb_page;
+struct wb_file;
+
+
+struct wb_conf {
+        uint64_t aggregate_size;
+        uint64_t window_size;
+        uint64_t disable_till;
+        gf_boolean_t enable_O_SYNC;
+        gf_boolean_t flush_behind;
+};
+
+
+typedef struct wb_local {
+        list_head_t winds;
+        struct wb_file *file;
+        list_head_t unwind_frames;
+        int op_ret;
+        int op_errno;
+        call_frame_t *frame;
+} wb_local_t;
+
+
+typedef struct write_request {
+        call_frame_t *frame;
+        off_t offset;
+        /*  int32_t op_ret;
+            int32_t op_errno; */
+        struct iovec *vector;
+        int32_t count;
+        dict_t *refs;
+        char write_behind;
+        char stack_wound;
+        char got_reply;
+        list_head_t list;
+        list_head_t winds;
+        /*  list_head_t unwinds;*/
+} wb_write_request_t;
+
+
+struct wb_file {
+        int disabled;
+        uint64_t disable_till;
+        off_t offset;
+        size_t window_size;
+        int32_t refcount;
+        int32_t op_ret;
+        int32_t op_errno;
+        list_head_t request;
+        fd_t *fd;
+        gf_lock_t lock;
+        xlator_t *this;
+};
+
+
+typedef struct wb_conf wb_conf_t;
+typedef struct wb_page wb_page_t;
+typedef struct wb_file wb_file_t;
+
+
+int32_t 
+wb_process_queue (call_frame_t *frame, wb_file_t *file, char flush_all);
+
+int32_t
+wb_sync (call_frame_t *frame, wb_file_t *file, list_head_t *winds);
+
+int32_t
+wb_sync_all (call_frame_t *frame, wb_file_t *file);
+
+int32_t 
+__wb_mark_winds (list_head_t *list, list_head_t *winds, size_t aggregate_size);
+
+
+wb_file_t *
+wb_file_create (xlator_t *this,
+                fd_t *fd)
+{
+        wb_file_t *file = NULL;
+        wb_conf_t *conf = this->private; 
+
+        file = CALLOC (1, sizeof (*file));
+        INIT_LIST_HEAD (&file->request);
+
+        /* fd_ref() not required, file should never decide the existance of
+         * an fd */
+        file->fd= fd;
+        file->disable_till = conf->disable_till;
+        file->this = this;
+        file->refcount = 1;
+
+        fd_ctx_set (fd, this, (uint64_t)(long)file);
+        
+        return file;
+}
+
+void
+wb_file_destroy (wb_file_t *file)
+{
+        int32_t refcount = 0;
+
+        LOCK (&file->lock);
+        {
+                refcount = --file->refcount;
+        }
+        UNLOCK (&file->lock);
+
+        if (!refcount){
+                LOCK_DESTROY (&file->lock);
+                FREE (file);
+        }
+
+        return;
+}
+
+
+int32_t
+wb_sync_cbk (call_frame_t *frame,
+             void *cookie,
+             xlator_t *this,
+             int32_t op_ret,
+             int32_t op_errno,
+             struct stat *stbuf)
+{
+        wb_local_t *local = NULL;
+        list_head_t *winds = NULL;
+        wb_file_t *file = NULL;
+        wb_write_request_t *request = NULL, *dummy = NULL;
+
+        local = frame->local;
+        winds = &local->winds;
+        file = local->file;
+
+        LOCK (&file->lock);
+        {
+                list_for_each_entry_safe (request, dummy, winds, winds) {
+                        request->got_reply = 1;
+                        if (!request->write_behind && (op_ret == -1)) {
+                                wb_local_t *per_request_local = request->frame->local;
+                                per_request_local->op_ret = op_ret;
+                                per_request_local->op_errno = op_errno;
+                        }
+
+                        /*
+                          request->op_ret = op_ret;
+                          request->op_errno = op_errno; 
+                        */
+                }
+        }
+        UNLOCK (&file->lock);
+
+        if (op_ret == -1)
+        {
+                file->op_ret = op_ret;
+                file->op_errno = op_errno;
+        }
+
+        wb_process_queue (frame, file, 0);  
+  
+        /* safe place to do fd_unref */
+        fd_unref (file->fd);
+
+        STACK_DESTROY (frame->root);
+
+        return 0;
+}
+
+int32_t
+wb_sync_all (call_frame_t *frame, wb_file_t *file) 
+{
+        list_head_t winds;
+        int32_t bytes = 0;
+
+        INIT_LIST_HEAD (&winds);
+
+        LOCK (&file->lock);
+        {
+                bytes = __wb_mark_winds (&file->request, &winds, 0);
+        }
+        UNLOCK (&file->lock);
+
+        wb_sync (frame, file, &winds);
+
+        return bytes;
+}
+
+
+int32_t
+wb_sync (call_frame_t *frame, wb_file_t *file, list_head_t *winds)
+{
+        wb_write_request_t *dummy = NULL, *request = NULL, *first_request = NULL, *next = NULL;
+        size_t total_count = 0, count = 0;
+        size_t copied = 0;
+        call_frame_t *sync_frame = NULL;
+        dict_t *refs = NULL;
+        wb_local_t *local = NULL;
+        struct iovec *vector = NULL;
+        int32_t bytes = 0;
+        size_t bytecount = 0;
+
+        list_for_each_entry (request, winds, winds)
+        {
+                total_count += request->count;
+                bytes += iov_length (request->vector, request->count);
+        }
+
+        if (!total_count) {
+                return 0;
+        }
+  
+        list_for_each_entry_safe (request, dummy, winds, winds) {
+                if (!vector) {
+                        vector = MALLOC (VECTORSIZE (MAX_VECTOR_COUNT));
+                        refs = get_new_dict ();
+        
+                        local = CALLOC (1, sizeof (*local));
+                        INIT_LIST_HEAD (&local->winds);
+            
+                        first_request = request;
+                }
+
+                count += request->count;
+                bytecount = VECTORSIZE (request->count);
+                memcpy (((char *)vector)+copied,
+                        request->vector,
+                        bytecount);
+                copied += bytecount;
+      
+                if (request->refs) {
+                        dict_copy (request->refs, refs);
+                }
+
+                next = NULL;
+                if (request->winds.next != winds) {    
+                        next = list_entry (request->winds.next, struct write_request, winds);
+                }
+
+                list_del_init (&request->winds);
+                list_add_tail (&request->winds, &local->winds);
+
+                if (!next || ((count + next->count) > MAX_VECTOR_COUNT)) {
+                        sync_frame = copy_frame (frame);  
+                        sync_frame->local = local;
+                        local->file = file;
+                        sync_frame->root->req_refs = dict_ref (refs);
+                        fd_ref (file->fd);
+                        STACK_WIND (sync_frame,
+                                    wb_sync_cbk,
+                                    FIRST_CHILD(sync_frame->this),
+                                    FIRST_CHILD(sync_frame->this)->fops->writev,
+                                    file->fd, vector,
+                                    count, first_request->offset);
+        
+                        dict_unref (refs);
+                        FREE (vector);
+                        first_request = NULL;
+                        refs = NULL;
+                        vector = NULL;
+                        copied = count = 0;
+                }
+        }
+
+        return bytes;
+}
+
+
+int32_t 
+wb_stat_cbk (call_frame_t *frame,
+             void *cookie,
+             xlator_t *this,
+             int32_t op_ret,
+             int32_t op_errno,
+             struct stat *buf)
+{
+        wb_local_t *local = NULL;
+  
+        local = frame->local;
+  
+        if (local->file)
+                fd_unref (local->file->fd);
+
+        STACK_UNWIND (frame, op_ret, op_errno, buf);
+
+        return 0;
+}
+
+
+int32_t
+wb_stat (call_frame_t *frame,
+         xlator_t *this,
+         loc_t *loc)
+{
+        wb_file_t *file = NULL;
+        fd_t *iter_fd = NULL;
+        wb_local_t *local = NULL;
+	uint64_t tmp_file = 0;
+
+        if (loc->inode)
+        {
+                iter_fd = fd_lookup (loc->inode, frame->root->pid);
+                if (iter_fd) {
+                        if (!fd_ctx_get (iter_fd, this, &tmp_file)) {
+				file = (wb_file_t *)(long)tmp_file;
+                        } else {
+                                fd_unref (iter_fd);
+                        }
+                }
+                if (file) {
+                        wb_sync_all (frame, file);
+                }
+        }
+
+        local = CALLOC (1, sizeof (*local));
+        local->file = file;
+
+        frame->local = local;
+
+        STACK_WIND (frame, wb_stat_cbk,
+                    FIRST_CHILD(this),
+                    FIRST_CHILD(this)->fops->stat,
+                    loc);
+        return 0;
+}
+
+
+int32_t 
+wb_fstat (call_frame_t *frame,
+          xlator_t *this,
+          fd_t *fd)
+{
+        wb_file_t *file = NULL;
+        wb_local_t *local = NULL;
+  	uint64_t tmp_file = 0;
+
+        if (fd_ctx_get (fd, this, &tmp_file)) {
+                gf_log (this->name, GF_LOG_ERROR, "returning EBADFD");
+                STACK_UNWIND (frame, -1, EBADFD, NULL);
+                return 0;
+        }
+
+	file = (wb_file_t *)(long)tmp_file;
+        if (file) {
+                fd_ref (file->fd);
+                wb_sync_all (frame, file);
+        }
+
+        local = CALLOC (1, sizeof (*local));
+        local->file = file;
+
+        frame->local = local;
+  
+        STACK_WIND (frame,
+                    wb_stat_cbk,
+                    FIRST_CHILD(this),
+                    FIRST_CHILD(this)->fops->fstat,
+                    fd);
+        return 0;
+}
+
+
+int32_t
+wb_truncate_cbk (call_frame_t *frame,
+                 void *cookie,
+                 xlator_t *this,
+                 int32_t op_ret,
+                 int32_t op_errno,
+                 struct stat *buf)
+{
+        wb_local_t *local = NULL; 
+  
+        local = frame->local;
+        if (local->file)
+                fd_unref (local->file->fd);
+
+        STACK_UNWIND (frame, op_ret, op_errno, buf);
+        return 0;
+}
+
+
+int32_t 
+wb_truncate (call_frame_t *frame,
+             xlator_t *this,
+             loc_t *loc,
+             off_t offset)
+{
+        wb_file_t *file = NULL;
+        fd_t *iter_fd = NULL;
+        wb_local_t *local = NULL;
+	uint64_t tmp_file = 0;
+
+        if (loc->inode)
+        {
+                iter_fd = fd_lookup (loc->inode, frame->root->pid);
+                if (iter_fd) {
+                        if (!fd_ctx_get (iter_fd, this, &tmp_file)){
+				file = (wb_file_t *)(long)tmp_file;
+                        } else {
+                                fd_unref (iter_fd);
+                        }
+                }
+    
+                if (file)
+                {
+                        wb_sync_all (frame, file);
+                }
+        }
+  
+        local = CALLOC (1, sizeof (*local));
+        local->file = file;
+
+        frame->local = local;
+
+        STACK_WIND (frame,
+                    wb_truncate_cbk,
+                    FIRST_CHILD(this),
+                    FIRST_CHILD(this)->fops->truncate,
+                    loc,
+                    offset);
+        return 0;
+}
+
+
+int32_t
+wb_ftruncate (call_frame_t *frame,
+              xlator_t *this,
+              fd_t *fd,
+              off_t offset)
+{
+        wb_file_t *file = NULL;
+        wb_local_t *local = NULL;
+	uint64_t tmp_file = 0;
+
+        if (fd_ctx_get (fd, this, &tmp_file)) {
+                gf_log (this->name, GF_LOG_ERROR, "returning EBADFD");
+                STACK_UNWIND (frame, -1, EBADFD, NULL);
+                return 0;
+        }
+
+	file = (wb_file_t *)(long)tmp_file;
+        if (file)
+                wb_sync_all (frame, file);
+
+        local = CALLOC (1, sizeof (*local));
+        local->file = file;
+
+        if (file)
+                fd_ref (file->fd);
+
+        frame->local = local;
+
+        STACK_WIND (frame,
+                    wb_truncate_cbk,
+                    FIRST_CHILD(this),
+                    FIRST_CHILD(this)->fops->ftruncate,
+                    fd,
+                    offset);
+        return 0;
+}
+
+
+int32_t 
+wb_utimens_cbk (call_frame_t *frame,
+                void *cookie,
+                xlator_t *this,
+                int32_t op_ret,
+                int32_t op_errno,
+                struct stat *buf)
+{
+        wb_local_t *local = NULL;       
+  
+        local = frame->local;
+        if (local->file)
+                fd_unref (local->file->fd);
+
+        STACK_UNWIND (frame, op_ret, op_errno, buf);
+        return 0;
+}
+
+
+int32_t 
+wb_utimens (call_frame_t *frame,
+            xlator_t *this,
+            loc_t *loc,
+            struct timespec tv[2])
+{
+        wb_file_t *file = NULL;
+        fd_t *iter_fd = NULL;
+        wb_local_t *local = NULL;
+	uint64_t tmp_file = 0;
+
+        if (loc->inode) {
+                iter_fd = fd_lookup (loc->inode, frame->root->pid);
+                if (iter_fd) {
+                        if (!fd_ctx_get (iter_fd, this, &tmp_file)) {
+				file = (wb_file_t *)(long)tmp_file;
+                        } else {
+                                fd_unref (iter_fd);
+                        }
+                }
+
+                if (file)
+                        wb_sync_all (frame, file);
+        }
+
+        local = CALLOC (1, sizeof (*local));
+        local->file = file;
+
+        frame->local = local;
+
+        STACK_WIND (frame,
+                    wb_utimens_cbk,
+                    FIRST_CHILD(this),
+                    FIRST_CHILD(this)->fops->utimens,
+                    loc,
+                    tv);
+        return 0;
+}
+
+int32_t
+wb_open_cbk (call_frame_t *frame,
+             void *cookie,
+             xlator_t *this,
+             int32_t op_ret,
+             int32_t op_errno,
+             fd_t *fd)
+{
+        int32_t flags = 0;
+        wb_file_t *file = NULL;
+        wb_conf_t *conf = this->private;
+
+        if (op_ret != -1)
+        {
+                file = wb_file_create (this, fd);
+
+                /* If mandatory locking has been enabled on this file,
+                   we disable caching on it */
+
+                if ((fd->inode->st_mode & S_ISGID) && !(fd->inode->st_mode & S_IXGRP))
+                        file->disabled = 1;
+
+                /* If O_DIRECT then, we disable chaching */
+                if (frame->local)
+                {
+                        flags = *((int32_t *)frame->local);
+                        if (((flags & O_DIRECT) == O_DIRECT) || 
+                            ((flags & O_RDONLY) == O_RDONLY) ||
+                            (((flags & O_SYNC) == O_SYNC) &&
+                             conf->enable_O_SYNC == _gf_true)) { 
+                                file->disabled = 1;
+                        }
+                }
+
+                LOCK_INIT (&file->lock);
+        }
+
+        STACK_UNWIND (frame, op_ret, op_errno, fd);
+        return 0;
+}
+
+
+int32_t
+wb_open (call_frame_t *frame,
+         xlator_t *this,
+         loc_t *loc,
+         int32_t flags,
+         fd_t *fd)
+{
+        frame->local = CALLOC (1, sizeof(int32_t));
+        *((int32_t *)frame->local) = flags;
+
+        STACK_WIND (frame,
+                    wb_open_cbk,
+                    FIRST_CHILD(this),
+                    FIRST_CHILD(this)->fops->open,
+                    loc, flags, fd);
+        return 0;
+}
+
+
+int32_t
+wb_create_cbk (call_frame_t *frame,
+               void *cookie,
+               xlator_t *this,
+               int32_t op_ret,
+               int32_t op_errno,
+               fd_t *fd,
+               inode_t *inode,
+               struct stat *buf)
+{
+        wb_file_t *file = NULL;
+
+        if (op_ret != -1)
+        {
+                file = wb_file_create (this, fd);
+                /* 
+                 * If mandatory locking has been enabled on this file,
+                 * we disable caching on it
+                 */
+                if ((fd->inode->st_mode & S_ISGID) && 
+                    !(fd->inode->st_mode & S_IXGRP))
+                {
+                        file->disabled = 1;
+                }
+
+                LOCK_INIT (&file->lock);
+        }
+
+        STACK_UNWIND (frame, op_ret, op_errno, fd, inode, buf);
+        return 0;
+}
+
+
+int32_t
+wb_create (call_frame_t *frame,
+           xlator_t *this,
+           loc_t *loc,
+           int32_t flags,
+           mode_t mode,
+           fd_t *fd)
+{
+        STACK_WIND (frame,
+                    wb_create_cbk,
+                    FIRST_CHILD(this),
+                    FIRST_CHILD(this)->fops->create,
+                    loc, flags, mode, fd);
+        return 0;
+}
+
+
+int32_t 
+__wb_cleanup_queue (wb_file_t *file)
+{
+        wb_write_request_t *request = NULL, *dummy = NULL;
+        int32_t bytes = 0;
+
+        list_for_each_entry_safe (request, dummy, &file->request, list)
+        {
+                if (request->got_reply && request->write_behind)
+                {
+                        bytes += iov_length (request->vector, request->count);
+                        list_del_init (&request->list);
+
+                        FREE (request->vector);
+                        dict_unref (request->refs);
+      
+                        FREE (request);
+                }
+        }
+
+        return bytes;
+}
+
+
+int32_t 
+__wb_mark_wind_all (list_head_t *list, list_head_t *winds)
+{
+        wb_write_request_t *request = NULL;
+        size_t size = 0;
+
+        list_for_each_entry (request, list, list)
+        {
+                if (!request->stack_wound)
+                {
+                        size += iov_length (request->vector, request->count);
+                        request->stack_wound = 1;
+                        list_add_tail (&request->winds, winds);
+                }
+        }
+  
+        return size;
+}
+
+
+size_t 
+__wb_get_aggregate_size (list_head_t *list)
+{
+        wb_write_request_t *request = NULL;
+        size_t size = 0;
+
+        list_for_each_entry (request, list, list)
+        {
+                if (!request->stack_wound)
+                {
+                        size += iov_length (request->vector, request->count);
+                }
+        }
+
+        return size;
+}
+
+uint32_t
+__wb_get_incomplete_writes (list_head_t *list)
+{
+        wb_write_request_t *request = NULL;
+        uint32_t count = 0;
+
+        list_for_each_entry (request, list, list)
+        {
+                if (request->stack_wound && !request->got_reply)
+                {
+                        count++;
+                }
+        }
+
+        return count;
+}
+
+int32_t
+__wb_mark_winds (list_head_t *list, list_head_t *winds, size_t aggregate_conf)
+{
+        size_t aggregate_current = 0;
+        uint32_t incomplete_writes = 0;
+
+        incomplete_writes = __wb_get_incomplete_writes (list); 
+
+        aggregate_current = __wb_get_aggregate_size (list);
+
+        if ((incomplete_writes == 0) || (aggregate_current >= aggregate_conf))
+        {
+                __wb_mark_wind_all (list, winds);
+        }
+
+        return aggregate_current;
+}
+
+
+size_t
+__wb_get_window_size (list_head_t *list)
+{
+        wb_write_request_t *request = NULL;
+        size_t size = 0;
+
+        list_for_each_entry (request, list, list)
+        {
+                if (request->write_behind && !request->got_reply)
+                {
+                        size += iov_length (request->vector, request->count);
+                }
+        }
+
+        return size;
+}
+
+
+size_t 
+__wb_mark_unwind_till (list_head_t *list, list_head_t *unwinds, size_t size)
+{
+        size_t written_behind = 0;
+        wb_write_request_t *request = NULL;
+
+        list_for_each_entry (request, list, list)
+        {
+                if (written_behind <= size)
+                {
+                        if (!request->write_behind)
+                        {
+                                wb_local_t *local = request->frame->local;
+                                written_behind += iov_length (request->vector, request->count);
+                                request->write_behind = 1;
+                                list_add_tail (&local->unwind_frames, unwinds);
+                        }
+                }
+                else
+                {
+                        break;
+                }
+        }
+
+        return written_behind;
+}
+
+
+int32_t 
+__wb_mark_unwinds (list_head_t *list, list_head_t *unwinds, size_t window_conf)
+{
+        size_t window_current = 0;
+
+        window_current = __wb_get_window_size (list);
+        if (window_current <= window_conf)
+        {
+                window_current += __wb_mark_unwind_till (list, unwinds,
+                                                         window_conf - window_current);
+        }
+
+        return window_current;
+}
+
+
+int32_t
+wb_stack_unwind (list_head_t *unwinds)
+{
+        struct stat buf = {0,};
+        wb_local_t *local = NULL, *dummy = NULL;
+
+        list_for_each_entry_safe (local, dummy, unwinds, unwind_frames)
+        {
+                list_del_init (&local->unwind_frames);
+                STACK_UNWIND (local->frame, local->op_ret, local->op_errno, &buf);
+        }
+
+        return 0;
+}
+
+
+int32_t
+wb_do_ops (call_frame_t *frame, wb_file_t *file, list_head_t *winds, list_head_t *unwinds)
+{
+        /* copy the frame before calling wb_stack_unwind, since this request containing current frame might get unwound */
+        /*  call_frame_t *sync_frame = copy_frame (frame); */
+ 
+        wb_stack_unwind (unwinds);
+        wb_sync (frame, file, winds);
+
+        return 0;
+}
+
+
+int32_t 
+wb_process_queue (call_frame_t *frame, wb_file_t *file, char flush_all) 
+{
+        list_head_t winds, unwinds;
+        size_t size = 0;
+        wb_conf_t *conf = file->this->private;
+
+        INIT_LIST_HEAD (&winds);
+        INIT_LIST_HEAD (&unwinds);
+
+        if (!file)
+        {
+                return -1;
+        }
+
+        size = flush_all ? 0 : conf->aggregate_size;
+        LOCK (&file->lock);
+        {
+                __wb_cleanup_queue (file);
+                __wb_mark_winds (&file->request, &winds, size);
+                __wb_mark_unwinds (&file->request, &unwinds, conf->window_size);
+        }
+        UNLOCK (&file->lock);
+
+        wb_do_ops (frame, file, &winds, &unwinds);
+        return 0;
+}
+
+
+wb_write_request_t *
+wb_enqueue (wb_file_t *file, 
+            call_frame_t *frame,
+            struct iovec *vector,
+            int32_t count,
+            off_t offset)
+{
+        wb_write_request_t *request = NULL;
+        wb_local_t *local = CALLOC (1, sizeof (*local));
+
+        request = CALLOC (1, sizeof (*request));
+
+        INIT_LIST_HEAD (&request->list);
+        INIT_LIST_HEAD (&request->winds);
+
+        request->frame = frame;
+        request->vector = iov_dup (vector, count);
+        request->count = count;
+        request->offset = offset;
+        request->refs = dict_ref (frame->root->req_refs);
+
+        frame->local = local;
+        local->frame = frame;
+        local->op_ret = iov_length (vector, count);
+        local->op_errno = 0;
+        INIT_LIST_HEAD (&local->unwind_frames);
+
+        LOCK (&file->lock);
+        {
+                list_add_tail (&request->list, &file->request);
+                file->offset = offset + iov_length (vector, count);
+        }
+        UNLOCK (&file->lock);
+
+        return request;
+}
+
+
+int32_t
+wb_writev_cbk (call_frame_t *frame,
+               void *cookie,
+               xlator_t *this,
+               int32_t op_ret,
+               int32_t op_errno,
+               struct stat *stbuf)
+{
+        STACK_UNWIND (frame, op_ret, op_errno, stbuf);
+        return 0;
+}
+
+
+int32_t
+wb_writev (call_frame_t *frame,
+           xlator_t *this,
+           fd_t *fd,
+           struct iovec *vector,
+           int32_t count,
+           off_t offset)
+{
+        wb_file_t *file = NULL;
+        char offset_expected = 1, wb_disabled = 0; 
+        call_frame_t *process_frame = NULL;
+        size_t size = 0;
+	uint64_t tmp_file = 0;
+
+        if (vector != NULL) 
+                size = iov_length (vector, count);
+
+        if (fd_ctx_get (fd, this, &tmp_file)) {
+                gf_log (this->name, GF_LOG_ERROR, "returning EBADFD");
+                STACK_UNWIND (frame, -1, EBADFD, NULL);
+                return 0;
+        }
+
+	file = (wb_file_t *)(long)tmp_file;
+        if (!file) {
+                gf_log (this->name, GF_LOG_ERROR,
+                        "wb_file not found for fd %p", fd);
+                STACK_UNWIND (frame, -1, EBADFD, NULL);
+                return 0;
+        }
+
+        LOCK (&file->lock);
+        {
+                if (file->disabled || file->disable_till) {
+                        if (size > file->disable_till) {
+                                file->disable_till = 0;
+                        } else {
+                                file->disable_till -= size;
+                        }
+                        wb_disabled = 1;
+                }
+
+                if (file->offset != offset)
+                        offset_expected = 0;
+        }
+        UNLOCK (&file->lock);
+
+        if (wb_disabled) {
+                STACK_WIND (frame,
+                            wb_writev_cbk,
+                            FIRST_CHILD (frame->this),
+                            FIRST_CHILD (frame->this)->fops->writev,
+                            file->fd,
+                            vector,
+                            count,
+                            offset);
+                return 0;
+        }
+
+        process_frame = copy_frame (frame);
+
+        if (!offset_expected)
+                wb_process_queue (process_frame, file, 1);
+
+        wb_enqueue (file, frame, vector, count, offset);
+        wb_process_queue (process_frame, file, 0);
+
+        STACK_DESTROY (process_frame->root);
+
+        return 0;
+}
+
+
+int32_t
+wb_readv_cbk (call_frame_t *frame,
+              void *cookie,
+              xlator_t *this,
+              int32_t op_ret,
+              int32_t op_errno,
+              struct iovec *vector,
+              int32_t count,
+              struct stat *stbuf)
+{
+        wb_local_t *local = NULL;
+
+        local = frame->local;
+
+        STACK_UNWIND (frame, op_ret, op_errno, vector, count, stbuf);
+        return 0;
+}
+
+
+int32_t
+wb_readv (call_frame_t *frame,
+          xlator_t *this,
+          fd_t *fd,
+          size_t size,
+          off_t offset)
+{
+        wb_file_t *file = NULL;
+        wb_local_t *local = NULL;
+	uint64_t tmp_file = 0;
+
+        if (fd_ctx_get (fd, this, &tmp_file)) {
+                gf_log (this->name, GF_LOG_ERROR, "returning EBADFD");
+                STACK_UNWIND (frame, -1, EBADFD, NULL);
+                return 0;
+        }
+
+	file = (wb_file_t *)(long)tmp_file;
+        if (file)
+                wb_sync_all (frame, file);
+
+        local = CALLOC (1, sizeof (*local));
+        local->file = file;
+
+        frame->local = local;
+
+        STACK_WIND (frame,
+                    wb_readv_cbk,
+                    FIRST_CHILD(this),
+                    FIRST_CHILD(this)->fops->readv,
+                    fd, size, offset);
+
+        return 0;
+}
+
+
+int32_t
+wb_ffr_bg_cbk (call_frame_t *frame,
+               void *cookie,
+               xlator_t *this,
+               int32_t op_ret,
+               int32_t op_errno)
+{
+        wb_local_t *local = NULL;
+        wb_file_t *file = NULL;
+
+        local = frame->local;
+        file = local->file;
+
+        if (file) {
+                fd_unref (file->fd);
+        }
+
+        if (file->op_ret == -1)
+        {
+                op_ret = file->op_ret;
+                op_errno = file->op_errno;
+
+                file->op_ret = 0;
+        }
+  
+        STACK_DESTROY (frame->root);
+        return 0;
+}
+
+
+int32_t
+wb_ffr_cbk (call_frame_t *frame,
+            void *cookie,
+            xlator_t *this,
+            int32_t op_ret,
+            int32_t op_errno)
+{
+        wb_local_t *local = NULL;
+        wb_file_t *file = NULL;
+
+        local = frame->local;
+        file = local->file;
+        if (file) {
+                /* corresponds to the fd_ref() done during wb_file_create() */
+                fd_unref (file->fd);
+        }
+
+        if (file->op_ret == -1)
+        {
+                op_ret = file->op_ret;
+                op_errno = file->op_errno;
+
+                file->op_ret = 0;
+        }
+
+        STACK_UNWIND (frame, op_ret, op_errno);
+        return 0;
+}
+
+
+int32_t
+wb_flush (call_frame_t *frame,
+          xlator_t *this,
+          fd_t *fd)
+{
+        wb_conf_t *conf = NULL;
+        wb_file_t *file = NULL;
+        call_frame_t *flush_frame = NULL;
+        wb_local_t *local = NULL;
+	uint64_t tmp_file = 0;
+
+        conf = this->private;
+
+        if (fd_ctx_get (fd, this, &tmp_file)) {
+                gf_log (this->name, GF_LOG_ERROR, "returning EBADFD");
+                STACK_UNWIND (frame, -1, EBADFD);
+                return 0;
+        }
+
+	file = (wb_file_t *)(long)tmp_file;
+
+        local = CALLOC (1, sizeof (*local));
+        local->file = file;
+        if (file)
+                fd_ref (file->fd);
+
+        if (&file->request != file->request.next) {
+                gf_log (this->name, GF_LOG_DEBUG,
+                        "request queue is not empty, it has to be synced");
+        }
+
+        if (conf->flush_behind && 
+	    (!file->disabled) && (file->disable_till == 0)) {
+                flush_frame = copy_frame (frame);     
+                STACK_UNWIND (frame, file->op_ret, 
+			      file->op_errno); // liar! liar! :O
+
+                flush_frame->local = local;
+                wb_sync_all (flush_frame, file);
+
+                STACK_WIND (flush_frame,
+                            wb_ffr_bg_cbk,
+                            FIRST_CHILD(this),
+                            FIRST_CHILD(this)->fops->flush,
+                            fd);
+        } else {
+                wb_sync_all (frame, file);
+
+                frame->local = local;
+                STACK_WIND (frame,
+                            wb_ffr_cbk,
+                            FIRST_CHILD(this),
+                            FIRST_CHILD(this)->fops->flush,
+                            fd);
+        }
+
+        return 0;
+}
+
+
+int32_t
+wb_fsync_cbk (call_frame_t *frame,
+              void *cookie,
+              xlator_t *this,
+              int32_t op_ret,
+              int32_t op_errno)
+{
+        wb_local_t *local = NULL;
+        wb_file_t *file = NULL;
+
+        local = frame->local;
+        file = local->file;
+
+        if (file->op_ret == -1)
+        {
+                op_ret = file->op_ret;
+                op_errno = file->op_errno;
+
+                file->op_ret = 0;
+        }
+
+        STACK_UNWIND (frame, op_ret, op_errno);
+        return 0;
+}
+
+int32_t
+wb_fsync (call_frame_t *frame,
+          xlator_t *this,
+          fd_t *fd,
+          int32_t datasync)
+{
+        wb_file_t *file = NULL;
+        wb_local_t *local = NULL;
+	uint64_t tmp_file = 0;
+
+        if (fd_ctx_get (fd, this, &tmp_file)) {
+                gf_log (this->name, GF_LOG_ERROR, "returning EBADFD");
+                STACK_UNWIND (frame, -1, EBADFD);
+                return 0;
+        }
+
+	file = (wb_file_t *)(long)tmp_file;
+        if (file)
+                wb_sync_all (frame, file);
+
+        local = CALLOC (1, sizeof (*local));
+        local->file = file;
+
+        frame->local = local;
+
+        STACK_WIND (frame,
+                    wb_fsync_cbk,
+                    FIRST_CHILD(this),
+                    FIRST_CHILD(this)->fops->fsync,
+                    fd, datasync);
+        return 0;
+}
+
+
+int32_t
+wb_release (xlator_t *this,
+            fd_t *fd)
+{
+        uint64_t file = 0;
+
+	fd_ctx_get (fd, this, &file);
+  	wb_file_destroy ((wb_file_t *)(long)file);
+
+        return 0;
+}
+
+
+int32_t 
+init (xlator_t *this)
+{
+        dict_t *options = NULL;
+        wb_conf_t *conf = NULL;
+        char *aggregate_size_string = NULL;
+        char *window_size_string    = NULL;
+        char *flush_behind_string   = NULL;
+        char *disable_till_string = NULL;
+        char *enable_O_SYNC_string = NULL;
+        int32_t ret = -1;
+
+        if ((this->children == NULL)
+            || this->children->next) {
+                gf_log (this->name, GF_LOG_ERROR,
+                        "FATAL: write-behind (%s) not configured with exactly one child",
+                        this->name);
+                return -1;
+        }
+
+        if (this->parents == NULL) {
+                gf_log (this->name, GF_LOG_WARNING,
+                        "dangling volume. check volfile");
+        }
+        
+        options = this->options;
+
+        conf = CALLOC (1, sizeof (*conf));
+        
+        conf->enable_O_SYNC = _gf_false;
+        ret = dict_get_str (options, "enable-O_SYNC",
+                            &enable_O_SYNC_string);
+        if (ret == 0) {
+                ret = gf_string2boolean (enable_O_SYNC_string,
+                                         &conf->enable_O_SYNC);
+                if (ret == -1) {
+                        gf_log (this->name, GF_LOG_ERROR,
+                                "'enable-O_SYNC' takes only boolean arguments");
+                        return -1;
+                }
+        }
+
+        /* configure 'options aggregate-size <size>' */
+        conf->aggregate_size = 0;
+        ret = dict_get_str (options, "block-size", 
+                            &aggregate_size_string);
+        if (ret == 0) {
+                ret = gf_string2bytesize (aggregate_size_string, 
+                                          &conf->aggregate_size);
+                if (ret != 0) {
+                        gf_log (this->name, GF_LOG_ERROR, 
+                                "invalid number format \"%s\" of \"option aggregate-size\"", 
+                                aggregate_size_string);
+                        return -1;
+                }
+        }
+
+        gf_log (this->name, GF_LOG_DEBUG,
+                "using aggregate-size = %"PRIu64"", 
+                conf->aggregate_size);
+  
+        conf->disable_till = 1;
+        ret = dict_get_str (options, "disable-for-first-nbytes", 
+                            &disable_till_string);
+        if (ret == 0) {
+                ret = gf_string2bytesize (disable_till_string, 
+                                          &conf->disable_till);
+                if (ret != 0) {
+                        gf_log (this->name, GF_LOG_ERROR, 
+                                "invalid number format \"%s\" of \"option disable-for-first-nbytes\"", 
+                                disable_till_string);
+                        return -1;
+                }
+        }
+
+        gf_log (this->name, GF_LOG_DEBUG,
+                "disabling write-behind for first %"PRIu64" bytes", 
+                conf->disable_till);
+  
+        /* configure 'option window-size <size>' */
+        conf->window_size = 0;
+        ret = dict_get_str (options, "cache-size", 
+                            &window_size_string);
+        if (ret == 0) {
+                ret = gf_string2bytesize (window_size_string, 
+                                          &conf->window_size);
+                if (ret != 0) {
+                        gf_log (this->name, GF_LOG_ERROR, 
+                                "invalid number format \"%s\" of \"option window-size\"", 
+                                window_size_string);
+                        FREE (conf);
+                        return -1;
+                }
+        }
+
+        if (!conf->window_size && conf->aggregate_size) {
+                gf_log (this->name, GF_LOG_WARNING,
+                        "setting window-size to be equal to aggregate-size(%"PRIu64")",
+                        conf->aggregate_size);
+                conf->window_size = conf->aggregate_size;
+        }
+
+        if (conf->window_size < conf->aggregate_size) {
+                gf_log (this->name, GF_LOG_ERROR,
+                        "aggregate-size(%"PRIu64") cannot be more than window-size"
+                        "(%"PRIu64")", conf->window_size, conf->aggregate_size);
+                FREE (conf);
+                return -1;
+        }
+
+        /* configure 'option flush-behind <on/off>' */
+        conf->flush_behind = 0;
+        ret = dict_get_str (options, "flush-behind", 
+                            &flush_behind_string);
+        if (ret == 0) {
+                ret = gf_string2boolean (flush_behind_string, 
+                                         &conf->flush_behind);
+                if (ret == -1) {
+                        gf_log (this->name, GF_LOG_ERROR,
+                                "'flush-behind' takes only boolean arguments");
+                        return -1;
+                }
+
+                if (conf->flush_behind) {
+			gf_log (this->name, GF_LOG_DEBUG,
+				"enabling flush-behind");
+                }
+        }
+        this->private = conf;
+        return 0;
+}
+
+
+void
+fini (xlator_t *this)
+{
+        wb_conf_t *conf = this->private;
+
+        FREE (conf);
+        return;
+}
+
+
+struct xlator_fops fops = {
+        .writev      = wb_writev,
+        .open        = wb_open,
+        .create      = wb_create,
+        .readv       = wb_readv,
+        .flush       = wb_flush,
+        .fsync       = wb_fsync,
+        .stat        = wb_stat,
+        .fstat       = wb_fstat,
+        .truncate    = wb_truncate,
+        .ftruncate   = wb_ftruncate,
+        .utimens     = wb_utimens,
+};
+
+struct xlator_mops mops = {
+};
+
+struct xlator_cbks cbks = {
+        .release  = wb_release
+};
+
+struct volume_options options[] = {
+        { .key  = {"flush-behind"}, 
+          .type = GF_OPTION_TYPE_BOOL
+        },
+        { .key  = {"block-size", "aggregate-size"}, 
+          .type = GF_OPTION_TYPE_SIZET, 
+          .min  = 128 * GF_UNIT_KB, 
+          .max  = 4 * GF_UNIT_MB 
+        },
+        { .key  = {"cache-size", "window-size"}, 
+          .type = GF_OPTION_TYPE_SIZET, 
+          .min  = 512 * GF_UNIT_KB, 
+          .max  = 1 * GF_UNIT_GB 
+        },
+        { .key = {"disable-for-first-nbytes"},
+          .type = GF_OPTION_TYPE_SIZET,
+          .min = 1,
+          .max = 1 * GF_UNIT_MB,
+        },
+        { .key = {"enable-O_SYNC"},
+          .type = GF_OPTION_TYPE_BOOL,
+        }, 
+        { .key = {NULL} },
+};