From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx150.postini.com [74.125.245.150]) by kanga.kvack.org (Postfix) with SMTP id 6D8BB6B0044 for ; Fri, 12 Oct 2012 03:48:06 -0400 (EDT) Message-ID: <5077CB29.2000505@parallels.com> Date: Fri, 12 Oct 2012 11:47:53 +0400 From: Glauber Costa MIME-Version: 1.0 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> In-Reply-To: <20121011134028.GH29295@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, Andrew Morton , Mel Gorman , Suleiman Souhlal , Tejun Heo , cgroups@vger.kernel.org, kamezawa.hiroyu@jp.fujitsu.com, Johannes Weiner , Greg Thelen , devel@openvz.org, Frederic Weisbecker , Christoph Lameter , Pekka Enberg 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! =) -- 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