From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f177.google.com (mail-lb0-f177.google.com [209.85.217.177]) by kanga.kvack.org (Postfix) with ESMTP id 938E16B0069 for ; Fri, 24 Oct 2014 09:40:26 -0400 (EDT) Received: by mail-lb0-f177.google.com with SMTP id w7so2593702lbi.36 for ; Fri, 24 Oct 2014 06:40:25 -0700 (PDT) Received: from gum.cmpxchg.org (gum.cmpxchg.org. [85.214.110.215]) by mx.google.com with ESMTPS id 2si7126102lal.27.2014.10.24.06.40.24 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 24 Oct 2014 06:40:24 -0700 (PDT) From: Johannes Weiner Subject: [patch] mm: memcontrol: shorten the page statistics update slowpath Date: Fri, 24 Oct 2014 09:40:20 -0400 Message-Id: <1414158020-25347-1-git-send-email-hannes@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Michal Hocko , Vladimir Davydov , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org While moving charges from one memcg to another, page stat updates must acquire the old memcg's move_lock to prevent double accounting. That situation is denoted by an increased memcg->move_accounting. However, the charge moving code declares this way too early for now, even before summing up the RSS and pre-allocating destination charges. Shorten this slowpath mode by increasing memcg->move_accounting only right before walking the task's address space with the intention of actually moving the pages. Signed-off-by: Johannes Weiner --- mm/memcontrol.c | 21 ++++++++------------- 1 file changed, 8 insertions(+), 13 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index c50176429fa3..23cf27cca370 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5263,8 +5263,6 @@ static void __mem_cgroup_clear_mc(void) static void mem_cgroup_clear_mc(void) { - struct mem_cgroup *from = mc.from; - /* * we must clear moving_task before waking up waiters at the end of * task migration. @@ -5275,8 +5273,6 @@ static void mem_cgroup_clear_mc(void) mc.from = NULL; mc.to = NULL; spin_unlock(&mc.lock); - - atomic_dec(&from->moving_account); } static int mem_cgroup_can_attach(struct cgroup_subsys_state *css, @@ -5310,15 +5306,6 @@ static int mem_cgroup_can_attach(struct cgroup_subsys_state *css, VM_BUG_ON(mc.moved_charge); VM_BUG_ON(mc.moved_swap); - /* - * Signal mem_cgroup_begin_page_stat() to take - * the memcg's move_lock while we're moving - * its pages to another memcg. Then wait for - * already started RCU-only updates to finish. - */ - atomic_inc(&from->moving_account); - synchronize_rcu(); - spin_lock(&mc.lock); mc.from = from; mc.to = memcg; @@ -5450,6 +5437,13 @@ static void mem_cgroup_move_charge(struct mm_struct *mm) struct vm_area_struct *vma; lru_add_drain_all(); + /* + * Signal mem_cgroup_begin_page_stat() to take the memcg's + * move_lock while we're moving its pages to another memcg. + * Then wait for already started RCU-only updates to finish. + */ + atomic_inc(&mc.from->moving_account); + synchronize_rcu(); retry: if (unlikely(!down_read_trylock(&mm->mmap_sem))) { /* @@ -5482,6 +5476,7 @@ retry: break; } up_read(&mm->mmap_sem); + atomic_dec(&mc.from->moving_account); } static void mem_cgroup_move_task(struct cgroup_subsys_state *css, -- 2.1.2 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org