Commit 019b4d12 authored by Richard Kennedy's avatar Richard Kennedy Committed by Linus Torvalds

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: default avatarRichard Kennedy <richard@rsk.demon.co.uk>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <jens.axboe@oracle.com>
Acked-by: default avatarNick Piggin <npiggin@suse.de>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: default avatarRik van Riel <riel@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 03affdef
...@@ -3265,7 +3265,7 @@ static void recalc_bh_state(void) ...@@ -3265,7 +3265,7 @@ static void recalc_bh_state(void)
struct buffer_head *alloc_buffer_head(gfp_t gfp_flags) 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) { if (ret) {
INIT_LIST_HEAD(&ret->b_assoc_buffers); INIT_LIST_HEAD(&ret->b_assoc_buffers);
get_cpu_var(bh_accounting).nr++; get_cpu_var(bh_accounting).nr++;
...@@ -3352,15 +3352,6 @@ int bh_submit_read(struct buffer_head *bh) ...@@ -3352,15 +3352,6 @@ int bh_submit_read(struct buffer_head *bh)
} }
EXPORT_SYMBOL(bh_submit_read); 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) void __init buffer_init(void)
{ {
int nrpages; int nrpages;
...@@ -3369,7 +3360,7 @@ void __init buffer_init(void) ...@@ -3369,7 +3360,7 @@ void __init buffer_init(void)
sizeof(struct buffer_head), 0, sizeof(struct buffer_head), 0,
(SLAB_RECLAIM_ACCOUNT|SLAB_PANIC| (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
SLAB_MEM_SPREAD), SLAB_MEM_SPREAD),
init_buffer_head); NULL);
/* /*
* Limit the bh occupancy to 10% of ZONE_NORMAL * Limit the bh occupancy to 10% of ZONE_NORMAL
......
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