[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, 2 insertions, 2 deletions

diff --git a/fs/dnotify.c b/fs/dnotify.c
index f3b540dd5d11..f932591df5a4 100644
--- a/fs/dnotify.c
+++ b/fs/dnotify.c
@@ -21,9 +21,9 @@
 #include <linux/spinlock.h>
 #include <linux/slab.h>
 
-int dir_notify_enable = 1;
+int dir_notify_enable __read_mostly = 1;
 
-static kmem_cache_t *dn_cache;
+static kmem_cache_t *dn_cache __read_mostly;
 
 static void redo_inode_mask(struct inode *inode)
 {