From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757881AbaE2QQi (ORCPT ); Thu, 29 May 2014 12:16:38 -0400 Received: from zene.cmpxchg.org ([85.214.230.12]:33609 "EHLO zene.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756289AbaE2QQe (ORCPT ); Thu, 29 May 2014 12:16:34 -0400 From: Johannes Weiner To: Andrew Morton Cc: Michal Hocko , Hugh Dickins , Tejun Heo , Vladimir Davydov , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [patch 08/10] mm: memcontrol: do not acquire page_cgroup lock for kmem pages Date: Thu, 29 May 2014 12:16:00 -0400 Message-Id: <1401380162-24121-9-git-send-email-hannes@cmpxchg.org> X-Mailer: git-send-email 1.9.3 In-Reply-To: <1401380162-24121-1-git-send-email-hannes@cmpxchg.org> References: <1401380162-24121-1-git-send-email-hannes@cmpxchg.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Kmem page charging and uncharging is serialized by means of exclusive access to the page. Do not take the page_cgroup lock and don't set pc->flags atomically. Signed-off-by: Johannes Weiner Acked-by: Michal Hocko Acked-by: Vladimir Davydov --- mm/memcontrol.c | 21 +++++++-------------- 1 file changed, 7 insertions(+), 14 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index f71eec597001..cd024dfb039a 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3455,12 +3455,13 @@ void __memcg_kmem_commit_charge(struct page *page, struct mem_cgroup *memcg, memcg_uncharge_kmem(memcg, PAGE_SIZE << order); return; } - + /* + * The page is freshly allocated and not visible to any + * outside callers yet. Set up pc non-atomically. + */ pc = lookup_page_cgroup(page); - lock_page_cgroup(pc); pc->mem_cgroup = memcg; - SetPageCgroupUsed(pc); - unlock_page_cgroup(pc); + pc->flags = PCG_USED; } void __memcg_kmem_uncharge_pages(struct page *page, int order) @@ -3470,19 +3471,11 @@ void __memcg_kmem_uncharge_pages(struct page *page, int order) pc = lookup_page_cgroup(page); - /* - * Fast unlocked return. Theoretically might have changed, have to - * check again after locking. - */ if (!PageCgroupUsed(pc)) return; - lock_page_cgroup(pc); - if (PageCgroupUsed(pc)) { - memcg = pc->mem_cgroup; - ClearPageCgroupUsed(pc); - } - unlock_page_cgroup(pc); + memcg = pc->mem_cgroup; + pc->flags = 0; /* * We trust that only if there is a memcg associated with the page, it -- 1.9.3