[PATCH] Use __read_mostly on some hot fs variables

I discovered on oprofile hunting on a SMP platform that dentry lookups were
slowed down because d_hash_mask, d_hash_shift and dentry_hashtable were in
a cache line that contained inodes_stat.  So each time inodes_stats is
changed by a cpu, other cpus have to refill their cache line.

This patch moves some variables to the __read_mostly section, in order to
avoid false sharing.  RCU dentry lookups can go full speed.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/pipe.c b/fs/pipe.c
index d976866a115b..4384c9290943 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -675,7 +675,7 @@ fail_page:
         return NULL;
 }
 
-static struct vfsmount *pipe_mnt;
+static struct vfsmount *pipe_mnt __read_mostly;
 static int pipefs_delete_dentry(struct dentry *dentry)
 {
         return 1;