From: Zhang Yanmin Date: Thu, 12 Feb 2009 16:00:17 +0000 (+0200) Subject: SLUB: Fix default slab order for big object sizes X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=e8120ff1ffc51102ead1f4c98a3fd5d26fefc722;p=linux-2.6-omap-h63xx.git SLUB: Fix default slab order for big object sizes The default order of kmalloc-8192 on 2*4 stoakley is an issue of calculate_order. slab_size order name ------------------------------------------------- 4096 3 sgpool-128 8192 2 kmalloc-8192 16384 3 kmalloc-16384 kmalloc-8192's default order is smaller than sgpool-128's. On 4*4 tigerton machine, a similiar issue appears on another kmem_cache. Function calculate_order uses 'min_objects /= 2;' to shrink. Plus size calculation/checking in slab_order, sometimes above issue appear. Below patch against 2.6.29-rc2 fixes it. I checked the default orders of all kmem_cache and they don't become smaller than before. So the patch wouldn't hurt performance. Signed-off-by Zhang Yanmin Signed-off-by: Pekka Enberg --- diff --git a/mm/slub.c b/mm/slub.c index 5a5e7f5bf79..c01a7a3001d 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1844,6 +1844,7 @@ static inline int calculate_order(int size) int order; int min_objects; int fraction; + int max_objects; /* * Attempt to find best configuration for a slab. This @@ -1856,6 +1857,9 @@ static inline int calculate_order(int size) min_objects = slub_min_objects; if (!min_objects) min_objects = 4 * (fls(nr_cpu_ids) + 1); + max_objects = (PAGE_SIZE << slub_max_order)/size; + min_objects = min(min_objects, max_objects); + while (min_objects > 1) { fraction = 16; while (fraction >= 4) { @@ -1865,7 +1869,7 @@ static inline int calculate_order(int size) return order; fraction /= 2; } - min_objects /= 2; + min_objects --; } /*