[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/fcntl.c b/fs/fcntl.c
index 03c789560fb8..2a2479196f96 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -412,7 +412,7 @@ out:
 
 /* Table to convert sigio signal codes into poll band bitmaps */
 
-static long band_table[NSIGPOLL] = {
+static const long band_table[NSIGPOLL] = {
         POLLIN | POLLRDNORM,                    /* POLL_IN */
         POLLOUT | POLLWRNORM | POLLWRBAND,      /* POLL_OUT */
         POLLIN | POLLRDNORM | POLLMSG,          /* POLL_MSG */
@@ -531,7 +531,7 @@ int send_sigurg(struct fown_struct *fown)
 }
 
 static DEFINE_RWLOCK(fasync_lock);
-static kmem_cache_t *fasync_cache;
+static kmem_cache_t *fasync_cache __read_mostly;
 
 /*
  * fasync_helper() is used by some character device drivers (mainly mice)