Posix: Optimize posix code to improve file creation

Problem: Before executing a fop in POSIX xlator it builds an internal
         path based on GFID.To validate the path it call's (l)stat
         system call and while .glusterfs is heavily loaded kernel takes
         time to lookup inode and due to that performance drops

Solution: In this patch we followed two ways to improve the performance.
          1) Keep open fd specific to first level directory(gfid[0])
             in .glusterfs, it would force to kernel keep the inodes
             from all those files in cache. In case of memory pressure
             kernel won't uncache first level inodes. We need to open
             256 fd's per brick to access the entry faster.
          2) Use at based call's to access relative path to reduce
             path based lookup time.

Note: To verify the patch we have executed kernel untar 100 times on 6
      different clients after enabling metadata group-cache and some
      other option.We were getting more than 20 percent improvement in
      kenel untar after applying the patch.

Credits: Xavi Hernandez <xhernandez@redhat.com>
Change-Id: I1643e6b01ed669b2bb148d02f4e6a8e08da45343
updates: #891
Signed-off-by: Mohit Agrawal <moagrawal@redhat.com>

3 files changed, 33 insertions, 0 deletions

diff --git a/libglusterfs/src/glusterfs/syscall.h b/libglusterfs/src/glusterfs/syscall.h
index 6b33c141a5e..91e921aea50 100644
--- a/libglusterfs/src/glusterfs/syscall.h
+++ b/libglusterfs/src/glusterfs/syscall.h
@@ -96,18 +96,27 @@ int
 sys_unlink(const char *pathname);
 
 int
+sys_unlinkat(int dfd, const char *pathname);
+
+int
 sys_rmdir(const char *pathname);
 
 int
 sys_symlink(const char *oldpath, const char *newpath);
 
 int
+sys_symlinkat(const char *oldpath, int dirfd, const char *newpath);
+
+int
 sys_rename(const char *oldpath, const char *newpath);
 
 int
 sys_link(const char *oldpath, const char *newpath);
 
 int
+sys_linkat(int oldfd, const char *oldpath, int newfd, const char *newpath);
+
+int
 sys_chmod(const char *path, mode_t mode);
 
 int
diff --git a/libglusterfs/src/libglusterfs.sym b/libglusterfs/src/libglusterfs.sym
index dc7382ba749..47e0872ca59 100644
--- a/libglusterfs/src/libglusterfs.sym
+++ b/libglusterfs/src/libglusterfs.sym
@@ -1039,6 +1039,7 @@ sys_futimes
 sys_lchown
 sys_lgetxattr
 sys_link
+sys_linkat
 sys_llistxattr
 sys_lremovexattr
 sys_lseek
@@ -1062,8 +1063,10 @@ sys_rmdir
 sys_stat
 sys_statvfs
 sys_symlink
+sys_symlinkat
 sys_truncate
 sys_unlink
+sys_unlinkat
 sys_utimensat
 sys_write
 sys_writev
diff --git a/libglusterfs/src/syscall.c b/libglusterfs/src/syscall.c
index 1d88c8adac1..49f782a837a 100644
--- a/libglusterfs/src/syscall.c
+++ b/libglusterfs/src/syscall.c
@@ -214,6 +214,15 @@ sys_unlink(const char *pathname)
 }
 
 int
+sys_unlinkat(int dfd, const char *pathname)
+{
+#ifdef GF_SOLARIS_HOST_OS
+    return FS_RET_CHECK0(solaris_unlinkat(dfd, pathname, 0), errno);
+#endif
+    return FS_RET_CHECK0(unlinkat(dfd, pathname, 0), errno);
+}
+
+int
 sys_rmdir(const char *pathname)
 {
     return FS_RET_CHECK0(rmdir(pathname), errno);
@@ -226,6 +235,12 @@ sys_symlink(const char *oldpath, const char *newpath)
 }
 
 int
+sys_symlinkat(const char *oldpath, int dirfd, const char *newpath)
+{
+    return FS_RET_CHECK0(symlinkat(oldpath, dirfd, newpath), errno);
+}
+
+int
 sys_rename(const char *oldpath, const char *newpath)
 {
 #ifdef GF_SOLARIS_HOST_OS
@@ -253,6 +268,12 @@ sys_link(const char *oldpath, const char *newpath)
 }
 
 int
+sys_linkat(int oldfd, const char *oldpath, int newfd, const char *newpath)
+{
+    return FS_RET_CHECK0(linkat(oldfd, oldpath, newfd, newpath, 0), errno);
+}
+
+int
 sys_chmod(const char *path, mode_t mode)
 {
     return FS_RET_CHECK0(chmod(path, mode), errno);