From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx115.postini.com [74.125.245.115]) by kanga.kvack.org (Postfix) with SMTP id 136AC6B005A for ; Fri, 17 Aug 2012 03:04:20 -0400 (EDT) Message-ID: <502DEC32.6070807@parallels.com> Date: Fri, 17 Aug 2012 11:01:06 +0400 From: Glauber Costa MIME-Version: 1.0 Subject: Re: [PATCH v2 08/11] memcg: disable kmem code when not in use. References: <1344517279-30646-1-git-send-email-glommer@parallels.com> <1344517279-30646-9-git-send-email-glommer@parallels.com> <20120817070241.GA18600@dhcp22.suse.cz> In-Reply-To: <20120817070241.GA18600@dhcp22.suse.cz> Content-Type: text/plain; charset="ISO-8859-1" 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 , Andrew Morton , kamezawa.hiroyu@jp.fujitsu.com, Christoph Lameter , David Rientjes , Pekka Enberg , Pekka Enberg , Suleiman Souhlal On 08/17/2012 11:02 AM, Michal Hocko wrote: > On Thu 09-08-12 17:01:16, Glauber Costa wrote: >> We can use jump labels to patch the code in or out when not used. >> >> Because the assignment: memcg->kmem_accounted = true is done after the >> jump labels increment, we guarantee that the root memcg will always be >> selected until all call sites are patched (see memcg_kmem_enabled). > > Not that it would be really important because kmem_accounted goes away > in a subsequent patch but I think the wording is a bit misleading here. > First of all there is no guanratee that kmem_accounted=true is seen > before atomic_inc(&key->enabled) because there is no memory barrier and > the lock serves just a leave barrier. But I do not think this is > important at all because key->enabled is what matters here. Even if > memcg_kmem_enabled is true we do not consider it if the key is disabled, > right? > Right. -- 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