[PATCH] fs: buffer_head, remove kmem_cache constructor to reduce memory usage under slub
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From: Richard Kennedy on 9 Feb 2010 08:40 fs: Remove the buffer_head 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(a)rsk.demon.co.uk> ---- This patch against 2.6.33-rc7 I've been running this patch for over a week on both a x86_64 desktop & a x86_32 laptop with no problems, only having fewer pages in the buffer_head cache :) regards Richard diff --git a/fs/buffer.c b/fs/buffer.c index 6fa5302..bc3212e 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |