Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753337Ab2JPItD (ORCPT ); Tue, 16 Oct 2012 04:49:03 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:60606 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753244Ab2JPItA (ORCPT ); Tue, 16 Oct 2012 04:49:00 -0400 X-SecurityPolicyCheck: OK by SHieldMailChecker v1.8.4 Message-ID: <507D1F5D.8080709@jp.fujitsu.com> Date: Tue, 16 Oct 2012 17:48:29 +0900 From: Kamezawa Hiroyuki User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:16.0) Gecko/20121010 Thunderbird/16.0.1 MIME-Version: 1.0 To: Glauber Costa CC: Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Mel Gorman , Suleiman Souhlal , Tejun Heo , cgroups@vger.kernel.org, Johannes Weiner , Greg Thelen , devel@openvz.org, Frederic Weisbecker , Christoph Lameter , Pekka Enberg Subject: Re: [PATCH v4 10/14] memcg: use static branches when code not in use References: <1349690780-15988-1-git-send-email-glommer@parallels.com> <1349690780-15988-11-git-send-email-glommer@parallels.com> <20121011134028.GH29295@dhcp22.suse.cz> <5077CB29.2000505@parallels.com> In-Reply-To: <5077CB29.2000505@parallels.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2823 Lines: 82 (2012/10/12 16:47), Glauber Costa wrote: > On 10/11/2012 05:40 PM, Michal Hocko wrote: >> On Mon 08-10-12 14:06:16, Glauber Costa wrote: >>> We can use static branches to patch the code in or out when not used. >>> >>> Because the _ACTIVE bit on kmem_accounted is only set after the >>> increment is done, we guarantee that the root memcg will always be >>> selected for kmem charges until all call sites are patched (see >>> memcg_kmem_enabled). This guarantees that no mischarges are applied. >>> >>> static branch decrement happens when the last reference count from the >>> kmem accounting in memcg dies. This will only happen when the charges >>> drop down to 0. >>> >>> When that happen, we need to disable the static branch only on those >>> memcgs that enabled it. To achieve this, we would be forced to >>> complicate the code by keeping track of which memcgs were the ones >>> that actually enabled limits, and which ones got it from its parents. >>> >>> It is a lot simpler just to do static_key_slow_inc() on every child >>> that is accounted. >>> >>> [ v4: adapted this patch to the changes in kmem_accounted ] >>> >>> Signed-off-by: Glauber Costa >>> CC: Kamezawa Hiroyuki >>> CC: Christoph Lameter >>> CC: Pekka Enberg >>> CC: Michal Hocko >>> CC: Johannes Weiner >>> CC: Suleiman Souhlal >> >> Looks reasonable to me >> Acked-by: Michal Hocko >> >> Just a little nit. >> >> [...] >> >>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >>> index 634c7b5..724a08b 100644 >>> --- a/mm/memcontrol.c >>> +++ b/mm/memcontrol.c >>> @@ -344,11 +344,15 @@ struct mem_cgroup { >>> /* internal only representation about the status of kmem accounting. */ >>> enum { >>> KMEM_ACCOUNTED_ACTIVE = 0, /* accounted by this cgroup itself */ >>> + KMEM_ACCOUNTED_ACTIVATED, /* static key enabled. */ >>> KMEM_ACCOUNTED_DEAD, /* dead memcg, pending kmem charges */ >>> }; >>> >>> -/* first bit */ >>> -#define KMEM_ACCOUNTED_MASK 0x1 >>> +/* >>> + * first two bits. We account when limit is on, but only after >>> + * call sites are patched >>> + */ >>> +#define KMEM_ACCOUNTED_MASK 0x3 >> >> The names are long but why not use KMEM_ACCOUNTED_ACTIVE* >> #define KMEM_ACCOUNTED_MASK 1<> > Because the names are long! =) > please use "long" macros ;) it's not bad. Anyway, Acked-by: KAMEZAWA Hiroyuki -- 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/