Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758553Ab0FJCxx (ORCPT ); Wed, 9 Jun 2010 22:53:53 -0400 Received: from fgwmail7.fujitsu.co.jp ([192.51.44.37]:41972 "EHLO fgwmail7.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750900Ab0FJCxw (ORCPT ); Wed, 9 Jun 2010 22:53:52 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Date: Thu, 10 Jun 2010 11:49:29 +0900 From: KAMEZAWA Hiroyuki To: Daisuke Nishimura Cc: "linux-mm@kvack.org" , "balbir@linux.vnet.ibm.com" , "linux-kernel@vger.kernel.org" Subject: Re: [RFC][PATCH] memcg remove css_get/put per pages v2 Message-Id: <20100610114929.1f3fc130.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20100610113424.d1037621.nishimura@mxp.nes.nec.co.jp> References: <20100608121901.3cab9bdf.kamezawa.hiroyu@jp.fujitsu.com> <20100609155940.dd121130.kamezawa.hiroyu@jp.fujitsu.com> <20100610113424.d1037621.nishimura@mxp.nes.nec.co.jp> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 3.0.2 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2362 Lines: 76 On Thu, 10 Jun 2010 11:34:24 +0900 Daisuke Nishimura wrote: > I can't find any trivial bugs from my review at the moment. > I'll do some tests. > Thank you for review. > Some minor commens. > > On Wed, 9 Jun 2010 15:59:40 +0900, KAMEZAWA Hiroyuki wrote: > > Still RFC, added lkml to CC: list. > > == > > From: KAMEZAWA Hiroyuki > > > > Now, memory cgroup increments css(cgroup subsys state)'s reference > > count per a charged page. And the reference count is kept until > > the page is uncharged. But this has 2 bad effect. > > > > 1. Because css_get/put calls atoimic_inc()/dec, heavy call of them > > on large smp will not scale well. > > 2. Because css's refcnt cannot be in a state as "ready-to-release", > > cgroup's notify_on_release handler can't work with memcg. > > > > This is a trial to remove css's refcnt per a page. Even if we remove > > refcnt, pre_destroy() does enough synchronization. > > > > After this patch, it seems css_get() is still called in try_charge(). > > But the logic is. > > > > 1. task_lock(mm->owner) > There is no task_lock() in this version :) > yes. > (snip) > > @@ -4219,7 +4252,6 @@ static int mem_cgroup_do_precharge(unsig > > mc.precharge += count; > > VM_BUG_ON(test_bit(CSS_ROOT, &mem->css.flags)); > > WARN_ON_ONCE(count > INT_MAX); > > - __css_get(&mem->css, (int)count); > > return ret; > > } > > one_by_one: > You can remove VM_BUG_ON() and WARN_ON_ONCE() here, too. > ok. > > @@ -4469,8 +4501,6 @@ static void mem_cgroup_clear_mc(void) > > */ > > res_counter_uncharge(&mc.to->res, > > PAGE_SIZE * mc.moved_swap); > > - VM_BUG_ON(test_bit(CSS_ROOT, &mc.to->css.flags)); > > - __css_put(&mc.to->css, mc.moved_swap); > > } > > /* we've already done mem_cgroup_get(mc.to) */ > > > > > And, you can remove "WARN_ON_ONCE(mc.moved_swap > INT_MAX)" at the beginning > of this block, too. > Hmm. ok. Ah...them, this patch fixes the limitation by "css's refcnt is int" problem. sounds nice. Thanks, -Kmae -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/