Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758472Ab0FJCtu (ORCPT ); Wed, 9 Jun 2010 22:49:50 -0400 Received: from TYO201.gate.nec.co.jp ([202.32.8.193]:64556 "EHLO tyo201.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750900Ab0FJCtt (ORCPT ); Wed, 9 Jun 2010 22:49:49 -0400 Date: Thu, 10 Jun 2010 11:34:24 +0900 From: Daisuke Nishimura To: KAMEZAWA Hiroyuki Cc: "linux-mm@kvack.org" , "balbir@linux.vnet.ibm.com" , "linux-kernel@vger.kernel.org" , Daisuke Nishimura Subject: Re: [RFC][PATCH] memcg remove css_get/put per pages v2 Message-Id: <20100610113424.d1037621.nishimura@mxp.nes.nec.co.jp> In-Reply-To: <20100609155940.dd121130.kamezawa.hiroyu@jp.fujitsu.com> References: <20100608121901.3cab9bdf.kamezawa.hiroyu@jp.fujitsu.com> <20100609155940.dd121130.kamezawa.hiroyu@jp.fujitsu.com> Organization: NEC Soft, 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: 2043 Lines: 60 I can't find any trivial bugs from my review at the moment. I'll do some tests. 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 :) (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. > @@ -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. Thanks, Daisuke Nishimura. -- 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/