performance/readdir-ahead: introduce directory read-ahead translator

This is a translator to improve the performance of typical,
sequential directory reads (i.e., ls). readdir-ahead begins
preloading the contents of a directory on open and serves readdir
requests from the preloaded content. readdir-ahead is currently
implemented to only handle the single threaded directory read
case.

readdir-ahead is currently disabled by default. It can be enabled
with the following command:

	gluster volume set <volname> readdir-ahead on

The following are results of a getdents test on a single brick
volume.

Test info:

- Single VM, gluster client/server.
- Volume mounted with native client using --gid-timeout=2.
- getdents on single directory with 100k 0-byte files.

Test results:

- !readdir-ahead

read 3120080 bytes from offset 0
3 MiB, 4348 ops, 0:00:07.00 (416.590 KiB/sec and 594.4737 ops/sec)

- readdir-ahead

read 3120080 bytes from offset 0
3 MiB, 4348 ops, 0:00:03.00 (820.116 KiB/sec and 1170.3043 ops/sec)

BUG: 980517
Change-Id: Ieceb9e1eb47d1d5b5af8da2bf03839537364653f
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-on: http://review.gluster.org/4519
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>

1 files changed, 46 insertions, 0 deletions

diff --git a/xlators/performance/readdir-ahead/src/readdir-ahead.h b/xlators/performance/readdir-ahead/src/readdir-ahead.h
new file mode 100644
index 000000000..e48786dae
--- /dev/null
+++ b/xlators/performance/readdir-ahead/src/readdir-ahead.h
@@ -0,0 +1,46 @@
+/*
+  Copyright (c) 2008-2013 Red Hat, Inc. <http://www.redhat.com>
+  This file is part of GlusterFS.
+
+  This file is licensed to you under your choice of the GNU Lesser
+  General Public License, version 3 or any later version (LGPLv3 or
+  later), or the GNU General Public License, version 2 (GPLv2), in all
+  cases as published by the Free Software Foundation.
+*/
+
+#ifndef __READDIR_AHEAD_H
+#define __READDIR_AHEAD_H
+
+/* state flags */
+#define RDA_FD_NEW	(1 << 0)
+#define RDA_FD_RUNNING	(1 << 1)
+#define RDA_FD_EOD	(1 << 2)
+#define RDA_FD_ERROR	(1 << 3)
+#define RDA_FD_BYPASS	(1 << 4)
+#define RDA_FD_PLUGGED	(1 << 5)
+
+struct rda_fd_ctx {
+	off_t cur_offset;	/* current head of the ctx */
+	size_t cur_size;	/* current size of the preload */
+	off_t next_offset;	/* tail of the ctx */
+	uint32_t state;
+	gf_lock_t lock;
+	gf_dirent_t entries;
+	call_frame_t *fill_frame;
+	call_stub_t *stub;
+	int op_errno;
+};
+
+struct rda_local {
+	struct rda_fd_ctx *ctx;
+	fd_t *fd;
+	off_t offset;
+};
+
+struct rda_priv {
+	uint32_t rda_req_size;
+	uint64_t rda_low_wmark;
+	uint64_t rda_high_wmark;
+};
+
+#endif /* __READDIR_AHEAD_H */