From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-la0-f49.google.com (mail-la0-f49.google.com [209.85.215.49]) by kanga.kvack.org (Postfix) with ESMTP id 05B846B0035 for ; Fri, 29 Nov 2013 05:09:34 -0500 (EST) Received: by mail-la0-f49.google.com with SMTP id er20so6503506lab.8 for ; Fri, 29 Nov 2013 02:09:33 -0800 (PST) Received: from relay.parallels.com (relay.parallels.com. [195.214.232.42]) by mx.google.com with ESMTPS id ji2si22165971lbc.126.2013.11.29.02.09.33 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Fri, 29 Nov 2013 02:09:33 -0800 (PST) Message-ID: <529867CE.4040004@parallels.com> Date: Fri, 29 Nov 2013 14:09:18 +0400 From: Vladimir Davydov MIME-Version: 1.0 Subject: Re: [PATCH] memcg: fix kmem_account_flags check in memcg_can_account_kmem() References: <1385567162-14973-1-git-send-email-vdavydov@parallels.com> <20131129094502.GD25893@dhcp22.suse.cz> In-Reply-To: <20131129094502.GD25893@dhcp22.suse.cz> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, devel@openvz.org, Johannes Weiner , Balbir Singh , KAMEZAWA Hiroyuki On 11/29/2013 01:45 PM, Michal Hocko wrote: > On Wed 27-11-13 19:46:01, Vladimir Davydov wrote: >> We should start kmem accounting for a memory cgroup only after both its >> kmem limit is set (KMEM_ACCOUNTED_ACTIVE) and related call sites are >> patched (KMEM_ACCOUNTED_ACTIVATED). > This should be vice-versa, no? ACTIVE is set after > static_key_slow_inc(&memcg_kmem_enabled_key) AFAICS. > >> Currently memcg_can_account_kmem() allows kmem accounting even if only >> one of the conditions is true. >> Fix it. > It would be nice to describe, what is the actual problem here. I assume > this is a charge vs. enable race. Let me try > > So we have KMEM_ACCOUNTED_ACTIVATED (set by memcg_update_cache_sizes) > but the static key is not enabled yet (so KMEM_ACCOUNTED_ACTIVE is not > set yet). memcg_can_account_kmem is called from 2 contexts during charge > - memcg_kmem_get_cache via __memcg_kmem_get_cache > - memcg_kmem_newpage_charge via __memcg_kmem_newpage_charge > > both of them start by checking memcg_kmem_enabled which is our > static key before memcg_can_account_kmem. This would suggest that > static_key+ACTIVE check memcg_can_account_kmem is sufficient. No? Yes, I guess you're perfectly right and we don't need the ACTIVATED bit at all. I'll look at this deeper and send a patch removing it if it doesn't break something. Thanks. -- 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