Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759753AbaD3XEG (ORCPT ); Wed, 30 Apr 2014 19:04:06 -0400 Received: from zene.cmpxchg.org ([85.214.230.12]:60018 "EHLO zene.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759678AbaD3XEA (ORCPT ); Wed, 30 Apr 2014 19:04:00 -0400 Date: Wed, 30 Apr 2014 19:03:50 -0400 From: Johannes Weiner To: Michal Hocko Cc: Andrew Morton , KAMEZAWA Hiroyuki , KOSAKI Motohiro , Greg Thelen , Michel Lespinasse , Tejun Heo , Hugh Dickins , Roman Gushchin , LKML , linux-mm@kvack.org Subject: Re: [PATCH 3/4] memcg, doc: clarify global vs. limit reclaims Message-ID: <20140430230350.GF26041@cmpxchg.org> References: <1398688005-26207-1-git-send-email-mhocko@suse.cz> <1398688005-26207-4-git-send-email-mhocko@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1398688005-26207-4-git-send-email-mhocko@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 28, 2014 at 02:26:44PM +0200, Michal Hocko wrote: > Be explicit about global and hard limit reclaims in our documentation. > > Signed-off-by: Michal Hocko > --- > Documentation/cgroups/memory.txt | 31 +++++++++++++++++-------------- > 1 file changed, 17 insertions(+), 14 deletions(-) > > diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt > index 4937e6fff9b4..add1be001416 100644 > --- a/Documentation/cgroups/memory.txt > +++ b/Documentation/cgroups/memory.txt > @@ -236,23 +236,26 @@ it by cgroup. > 2.5 Reclaim > > Each cgroup maintains a per cgroup LRU which has the same structure as > -global VM. When a cgroup goes over its limit, we first try > -to reclaim memory from the cgroup so as to make space for the new > -pages that the cgroup has touched. If the reclaim is unsuccessful, > -an OOM routine is invoked to select and kill the bulkiest task in the > -cgroup. (See 10. OOM Control below.) > - > -The reclaim algorithm has not been modified for cgroups, except that > -pages that are selected for reclaiming come from the per-cgroup LRU > -list. > - > -NOTE: Reclaim does not work for the root cgroup, since we cannot set any > -limits on the root cgroup. > +global VM. Cgroups can get reclaimed basically under two conditions > + - under global memory pressure when all cgroups are reclaimed > + proportionally wrt. their LRU size in a round robin fashion > + - when a cgroup or its hierarchical parent (see 6. Hierarchical support) > + hits hard limit. If the reclaim is unsuccessful, an OOM routine is invoked > + to select and kill the bulkiest task in the cgroup. (See 10. OOM Control > + below.) In the whole hierarchy, not just that cgroup. > +Global and hard-limit reclaims share the same code the only difference > +is the objective of the reclaim. The global reclaim aims at balancing > +zones' watermarks while the limit reclaim frees some memory to allow new > +charges. This is a kswapd vs. direct reclaim issue, not global vs. memcg. Memcg reclaim just happens to be direct reclaim. Either way, I'd rather not have such implementation details in the user documentation. > +NOTE: Hard limit reclaim does not work for the root cgroup, since we cannot set > +any limits on the root cgroup. Not sure it's necessary to include this... -- 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/