From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id 836CF6B01E4 for ; Mon, 15 Mar 2010 10:48:41 -0400 (EDT) Date: Mon, 15 Mar 2010 10:48:03 -0400 From: Vivek Goyal Subject: Re: [PATCH -mmotm 0/5] memcg: per cgroup dirty limit (v6) Message-ID: <20100315144803.GG21127@redhat.com> References: <1268175636-4673-1-git-send-email-arighi@develer.com> <20100311093913.07c9ca8a.kamezawa.hiroyu@jp.fujitsu.com> <20100311101726.f58d24e9.kamezawa.hiroyu@jp.fujitsu.com> <1268298865.5279.997.camel@twins> <20100311182500.0f3ba994.kamezawa.hiroyu@jp.fujitsu.com> <20100311184244.6735076a.kamezawa.hiroyu@jp.fujitsu.com> <20100312101411.b2639128.nishimura@mxp.nes.nec.co.jp> <20100312112433.689c7294.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100312112433.689c7294.kamezawa.hiroyu@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki Cc: Daisuke Nishimura , Peter Zijlstra , Andrea Righi , Balbir Singh , Trond Myklebust , Suleiman Souhlal , Greg Thelen , "Kirill A. Shutemov" , Andrew Morton , containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Fri, Mar 12, 2010 at 11:24:33AM +0900, KAMEZAWA Hiroyuki wrote: > On Fri, 12 Mar 2010 10:14:11 +0900 > Daisuke Nishimura wrote: > > > On Thu, 11 Mar 2010 18:42:44 +0900, KAMEZAWA Hiroyuki wrote: > > > On Thu, 11 Mar 2010 18:25:00 +0900 > > > KAMEZAWA Hiroyuki wrote: > > > > Then, it's not problem that check pc->mem_cgroup is root cgroup or not > > > > without spinlock. > > > > == > > > > void mem_cgroup_update_stat(struct page *page, int idx, bool charge) > > > > { > > > > pc = lookup_page_cgroup(page); > > > > if (unlikely(!pc) || mem_cgroup_is_root(pc->mem_cgroup)) > > > > return; > > > > ... > > > > } > > > > == > > > > This can be handle in the same logic of "lock failure" path. > > > > And we just do ignore accounting. > > > > > > > > There are will be no spinlocks....to do more than this, > > > > I think we have to use "struct page" rather than "struct page_cgroup". > > > > > > > Hmm..like this ? The bad point of this patch is that this will corrupt FILE_MAPPED > > > status in root cgroup. This kind of change is not very good. > > > So, one way is to use this kind of function only for new parameters. Hmm. > > IMHO, if we disable accounting file stats in root cgroup, it would be better > > not to show them in memory.stat to avoid confusing users. > agreed. > > > But, hmm, I think accounting them in root cgroup isn't so meaningless. > > Isn't making mem_cgroup_has_dirty_limit() return false in case of root cgroup enough? > > > The problem is spinlock overhead. > > IMHO, there are 2 excuse for "not accounting" in root cgroup > 1. Low overhead is always appreciated. > 2. Root's statistics can be obtained by "total - sum of children". > IIUC, Total sum of children works only if user_hierarchy=1? At the same time it does not work if there tasks in root cgroup and not in children group. Vivek -- 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