From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754102Ab2CUFYt (ORCPT ); Wed, 21 Mar 2012 01:24:49 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:41596 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751035Ab2CUFYs (ORCPT ); Wed, 21 Mar 2012 01:24:48 -0400 X-SecurityPolicyCheck: OK by SHieldMailChecker v1.7.4 Message-ID: <4F6965AC.4070004@jp.fujitsu.com> Date: Wed, 21 Mar 2012 14:22:52 +0900 From: KAMEZAWA Hiroyuki User-Agent: Mozilla/5.0 (Windows NT 6.0; rv:10.0.2) Gecko/20120216 Thunderbird/10.0.2 MIME-Version: 1.0 To: "Aneesh Kumar K.V" CC: Glauber Costa , linux-mm@kvack.org, mgorman@suse.de, dhillf@gmail.com, aarcange@redhat.com, mhocko@suse.cz, akpm@linux-foundation.org, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org Subject: Re: [PATCH -V4 04/10] memcg: Add HugeTLB extension References: <1331919570-2264-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1331919570-2264-5-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <4F669C2E.1010502@jp.fujitsu.com> <874ntlkrp6.fsf@linux.vnet.ibm.com> <4F66D993.2080100@jp.fujitsu.com> <4F671AE6.5020204@parallels.com>User-Agent: Notmuch/0.11.1+346~g13d19c3 (http://notmuchmail.org) Emacs/23.3.1 (x86_64-pc-linux-gnu) <87obrqsgno.fsf@linux.vnet.ibm.com> In-Reply-To: <87obrqsgno.fsf@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2012/03/21 13:48), Aneesh Kumar K.V wrote: > Glauber Costa writes: > >> On 03/19/2012 11:00 AM, KAMEZAWA Hiroyuki wrote: >>> (2012/03/19 15:52), Aneesh Kumar K.V wrote: >>> >>>> >>>>>> +#ifdef CONFIG_MEM_RES_CTLR_HUGETLB >>>>>> +static bool mem_cgroup_have_hugetlb_usage(struct mem_cgroup *memcg) >>>>>> +{ >>>>>> + int idx; >>>>>> + for (idx = 0; idx< hugetlb_max_hstate; idx++) { >>>>>> + if (memcg->hugepage[idx].usage> 0) >>>>>> + return 1; >>>>>> + } >>>>>> + return 0; >>>>>> +} >>>>> >>>>> >>>>> Please use res_counter_read_u64() rather than reading the value directly. >>>>> >>>> >>>> The open-coded variant is mostly derived from mem_cgroup_force_empty. I >>>> have updated the patch to use res_counter_read_u64. >>>> >>> >>> Ah, ok. it's(maybe) my bad. I'll schedule a fix. >>> >> Kame, >> >> I actually have it ready here. I can submit it if you want. >> >> This one has bitten me as well when I was trying to experiment with the >> res_counter performance... > > Do we really need memcg.res.usage to be accurate in that while loop ? If > we miss a zero update because we encountered a partial update; in the > next loop we will find it zero right ? > At rmdir(), I assume there is no task in memcg. It means res->usage never increase and no other thread than force_empty will touch res->counter. So, I think memcg->res.usage > 0 never be wrong and we'll find correct comparison by continuing the loop. But recent kmem accounting at el may break the assumption (I'm not fully sure..) So, I think it will be good to use res_counter_u64(). This part is not important for performance, anyway. Thanks, -Kame