[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/namespace.c b/fs/namespace.c
index 71e75bcf4d28..e069a4c5e389 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -43,9 +43,9 @@ __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock);
 
 static int event;
 
-static struct list_head *mount_hashtable;
+static struct list_head *mount_hashtable __read_mostly;
 static int hash_mask __read_mostly, hash_bits __read_mostly;
-static kmem_cache_t *mnt_cache;
+static kmem_cache_t *mnt_cache __read_mostly;
 static struct rw_semaphore namespace_sem;
 
 /* /sys/fs */