From 9b2cd506e5f2117f94c28a0040bf5da058105316 Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Mon, 14 Apr 2008 19:11:41 +0300 Subject: [PATCH] slub: Calculate min_objects based on number of processors. The mininum objects per slab is calculated based on the number of processors that may come online. Processors min_objects --------------------------- 1 8 2 12 4 16 8 20 16 24 32 28 64 32 1024 48 4096 56 The higher the number of processors the large the order sizes used for various slab caches will become. This has been shown to address the performance issues in hackbench on 16p etc. The calculation is only performed if slub_min_objects is zero (default). If one specifies a slub_min_objects on boot then that setting is taken. As suggested by Zhang Yanmin's performance tests on 16-core Tigerton, use the formula '4 * (fls(nr_cpu_ids) + 1)': ./hackbench 100 process 2000: 1) 2.6.25-rc6slab: 23.5 seconds 2) 2.6.25-rc7SLUB+slub_min_objects=20: 31 seconds 3) 2.6.25-rc7SLUB+slub_min_objects=24: 23.5 seconds Signed-off-by: Christoph Lameter Signed-off-by: Zhang Yanmin Signed-off-by: Pekka Enberg --- mm/slub.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/slub.c b/mm/slub.c index 6572cef0c43..e2e6ba7a517 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1803,7 +1803,7 @@ static struct page *get_object_page(const void *x) */ static int slub_min_order; static int slub_max_order = PAGE_ALLOC_COSTLY_ORDER; -static int slub_min_objects = 4; +static int slub_min_objects; /* * Merge control. If this is set then no merging of slab caches will occur. @@ -1880,6 +1880,8 @@ static inline int calculate_order(int size) * we reduce the minimum objects required in a slab. */ min_objects = slub_min_objects; + if (!min_objects) + min_objects = 4 * (fls(nr_cpu_ids) + 1); while (min_objects > 1) { fraction = 8; while (fraction >= 4) { -- 2.20.1