From: Richard Kennedy Date: Wed, 10 Mar 2010 23:20:33 +0000 (-0800) Subject: fs: buffer_head: remove kmem_cache constructor to reduce memory usage under slub X-Git-Tag: firefly_0821_release~9833^2~2818 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=019b4d123aa7b9fc135b532e021cfde85db7665d;p=firefly-linux-kernel-4.4.55.git 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 Cc: Alexander Viro Cc: Jens Axboe Acked-by: Nick Piggin Cc: "Theodore Ts'o" Reviewed-by: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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