From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx147.postini.com [74.125.245.147]) by kanga.kvack.org (Postfix) with SMTP id F14066B009D for ; Mon, 15 Jul 2013 02:32:31 -0400 (EDT) Received: by mail-la0-f42.google.com with SMTP id eb20so9189782lab.1 for ; Sun, 14 Jul 2013 23:32:30 -0700 (PDT) Date: Mon, 15 Jul 2013 10:32:26 +0400 From: Glauber Costa Subject: Re: [PATCH V4 5/6] memcg: patch mem_cgroup_{begin,end}_update_page_stat() out if only root memcg exists Message-ID: <20130715063224.GA3745@localhost.localdomain> References: <1373044710-27371-1-git-send-email-handai.szj@taobao.com> <1373045623-27712-1-git-send-email-handai.szj@taobao.com> <20130711145625.GK21667@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Sha Zhengju Cc: Michal Hocko , "linux-mm@kvack.org" , Cgroups , Greg Thelen , KAMEZAWA Hiroyuki , Andrew Morton , Wu Fengguang , Mel Gorman , Sha Zhengju On Fri, Jul 12, 2013 at 09:13:56PM +0800, Sha Zhengju wrote: > Ooops.... it seems unreachable, change Glauber's email... > > > On Fri, Jul 12, 2013 at 8:59 PM, Sha Zhengju wrote: > > > Add cc to Glauber > > Thanks > > > > On Thu, Jul 11, 2013 at 10:56 PM, Michal Hocko wrote: > > > On Sat 06-07-13 01:33:43, Sha Zhengju wrote: > > >> From: Sha Zhengju > > >> > > >> If memcg is enabled and no non-root memcg exists, all allocated > > >> pages belongs to root_mem_cgroup and wil go through root memcg > > >> statistics routines. So in order to reduce overheads after adding > > >> memcg dirty/writeback accounting in hot paths, we use jump label to > > >> patch mem_cgroup_{begin,end}_update_page_stat() in or out when not > > >> used. > > > > > > I do not think this is enough. How much do you save? One atomic read. > > > This doesn't seem like a killer. > > > > > > I hoped we could simply not account at all and move counters to the root > > > cgroup once the label gets enabled. > > > > I have thought of this approach before, but it would probably run into > > another issue, e.g, each zone has a percpu stock named ->pageset to > > optimize the increment and decrement operations, and I haven't figure out a > > simpler and cheaper approach to handle that stock numbers if moving global > > counters to root cgroup, maybe we can just leave them and can afford the > > approximation? > > > > Glauber have already done lots of works here, in his previous patchset he > > also tried to move some global stats to root ( > > http://comments.gmane.org/gmane.linux.kernel.cgroups/6291). May I steal > > some of your ideas here, Glauber? :P > > Of course. Please go ahead and keep me posted in my new address. -- 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