From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx167.postini.com [74.125.245.167]) by kanga.kvack.org (Postfix) with SMTP id 617476B0002 for ; Wed, 15 May 2013 08:35:13 -0400 (EDT) Received: by mail-lb0-f171.google.com with SMTP id v20so1784145lbc.2 for ; Wed, 15 May 2013 05:35:11 -0700 (PDT) Message-ID: <519380FC.1040504@openvz.org> Date: Wed, 15 May 2013 16:35:08 +0400 From: Konstantin Khlebnikov MIME-Version: 1.0 Subject: Re: [PATCH V2 0/3] memcg: simply lock of page stat accounting References: <1368421410-4795-1-git-send-email-handai.szj@taobao.com> In-Reply-To: <1368421410-4795-1-git-send-email-handai.szj@taobao.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Sha Zhengju Cc: cgroups@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.cz, kamezawa.hiroyu@jp.fujitsu.com, akpm@linux-foundation.org, hughd@google.com, gthelen@google.com, Sha Zhengju Sha Zhengju wrote: > Hi, > > This is my second attempt to make memcg page stat lock simpler, the > first version: http://www.spinics.net/lists/linux-mm/msg50037.html. > > In this version I investigate the potential race conditions among > page stat, move_account, charge, uncharge and try to prove it race > safe of my proposing lock scheme. The first patch is the basis of > the patchset, so if I've made some stupid mistake please do not > hesitate to point it out. I have a provocational question. Who needs these numbers? I mean per-cgroup nr_mapped and so on. It's too hard to maintain them carefully and I don't know any clear usage for them. I have written several implementations of this stuff for openvz kernel. But at the end I have decided to just remove it. Do anybody knows really useful use cases for these nr_mapped counters? In our kernel we have per-container nr_dirty and nr_writeback counters. Bit they are implemented on top of radix-tree tags, and their owners are stored on inode/mapping. So, this is completely different story. I definitely have missed some discussions about these questions. Or not? I hope it's a good time to return. > > Change log: > v2<- v1: > * rewrite comments on race condition > * split orignal large patch to two parts > * change too heavy try_get_mem_cgroup_from_page() to rcu_read_lock > to hold memcg alive > > Sha Zhengju (3): > memcg: rewrite the comment about race condition of page stat accounting > memcg: alter mem_cgroup_{update,inc,dec}_page_stat() args to memcg pointer > memcg: simplify lock of memcg page stat account > > include/linux/memcontrol.h | 14 ++++++------- > mm/memcontrol.c | 16 ++++++--------- > mm/rmap.c | 49 +++++++++++++++++++++++++++++++++----------- > 3 files changed, 50 insertions(+), 29 deletions(-) > > -- > 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 -- 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