From 130655ef097940b627e8e04fa7c6f3b51cf24f85 Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Tue, 23 Aug 2011 08:36:59 +0800 Subject: slub: add slab with one free object to partial list tail The slab has just one free object, adding it to partial list head doesn't make sense. And it can cause lock contentation. For example, 1. CPU takes the slab from partial list 2. fetch an object 3. switch to another slab 4. free an object, then the slab is added to partial list again In this way n->list_lock will be heavily contended. In fact, Alex had a hackbench regression. 3.1-rc1 performance drops about 70% against 3.0. This patch fixes it. Acked-by: Christoph Lameter Reported-by: Alex Shi Signed-off-by: Shaohua Li Signed-off-by: Shaohua Li Signed-off-by: Pekka Enberg --- mm/slub.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'mm') diff --git a/mm/slub.c b/mm/slub.c index 9f662d70eb47..7c54fe83a90c 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2377,7 +2377,7 @@ static void __slab_free(struct kmem_cache *s, struct page *page, */ if (unlikely(!prior)) { remove_full(s, page); - add_partial(n, page, 0); + add_partial(n, page, 1); stat(s, FREE_ADD_PARTIAL); } } -- cgit v1.2.3