[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>
diff --git a/fs/bio.c b/fs/bio.c
index 73e664c..49db928 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -30,7 +30,7 @@
#define BIO_POOL_SIZE 256
-static kmem_cache_t *bio_slab;
+static kmem_cache_t *bio_slab __read_mostly;
#define BIOVEC_NR_POOLS 6
@@ -39,7 +39,7 @@
* basically we just need to survive
*/
#define BIO_SPLIT_ENTRIES 8
-mempool_t *bio_split_pool;
+mempool_t *bio_split_pool __read_mostly;
struct biovec_slab {
int nr_vecs;
