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authorRichard Kennedy <richard@rsk.demon.co.uk>2010-03-10 15:20:33 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2010-03-12 15:52:27 -0800
commit019b4d123aa7b9fc135b532e021cfde85db7665d (patch)
tree91edbae535136417bc1277dd2c40d98c7ea7ec8f
parent03affdef4fc85e416e3862abb0aa549c6034cdd0 (diff)
fs: buffer_head: remove kmem_cache constructor to reduce memory usage under slub
When using slub, having a kmem_cache constructor forces slub to add a free pointer to the size of the cached object, which can have a significant impact to the number of small objects that can fit into a slab. As buffer_head is relatively small and we can have large numbers of them, removing the constructor is a definite win. On x86_64 removing the constructor gives me 39 objects/slab, 3 more than without the patch. And on x86_32 73 objects/slab, which is 9 more. As alloc_buffer_head() already initializes each new object there is very little difference in actual code run. Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Jens Axboe <jens.axboe@oracle.com> Acked-by: Nick Piggin <npiggin@suse.de> Cc: "Theodore Ts'o" <tytso@mit.edu> Reviewed-by: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/buffer.c13
1 files changed, 2 insertions, 11 deletions
diff --git a/fs/buffer.c b/fs/buffer.c
index 6fa530256bfd..bc3212e0cef9 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3265,7 +3265,7 @@ static void recalc_bh_state(void)
struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
{
- struct buffer_head *ret = kmem_cache_alloc(bh_cachep, gfp_flags);
+ struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
if (ret) {
INIT_LIST_HEAD(&ret->b_assoc_buffers);
get_cpu_var(bh_accounting).nr++;
@@ -3352,15 +3352,6 @@ int bh_submit_read(struct buffer_head *bh)
}
EXPORT_SYMBOL(bh_submit_read);
-static void
-init_buffer_head(void *data)
-{
- struct buffer_head *bh = data;
-
- memset(bh, 0, sizeof(*bh));
- INIT_LIST_HEAD(&bh->b_assoc_buffers);
-}
-
void __init buffer_init(void)
{
int nrpages;
@@ -3369,7 +3360,7 @@ void __init buffer_init(void)
sizeof(struct buffer_head), 0,
(SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
SLAB_MEM_SPREAD),
- init_buffer_head);
+ NULL);
/*
* Limit the bh occupancy to 10% of ZONE_NORMAL