Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932272AbaD1M2l (ORCPT ); Mon, 28 Apr 2014 08:28:41 -0400 Received: from cantor2.suse.de ([195.135.220.15]:57826 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932076AbaD1M1I (ORCPT ); Mon, 28 Apr 2014 08:27:08 -0400 From: Michal Hocko To: Johannes Weiner , Andrew Morton , KAMEZAWA Hiroyuki Cc: KOSAKI Motohiro , Greg Thelen , Michel Lespinasse , Tejun Heo , Hugh Dickins , Roman Gushchin , LKML , Subject: [PATCH 3/4] memcg, doc: clarify global vs. limit reclaims Date: Mon, 28 Apr 2014 14:26:44 +0200 Message-Id: <1398688005-26207-4-git-send-email-mhocko@suse.cz> X-Mailer: git-send-email 2.0.0.rc0 In-Reply-To: <1398688005-26207-1-git-send-email-mhocko@suse.cz> References: <1398688005-26207-1-git-send-email-mhocko@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.) + +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. + +NOTE: Hard limit reclaim does not work for the root cgroup, since we cannot set +any limits on the root cgroup. Note2: When panic_on_oom is set to "2", the whole system will panic. -When oom event notifier is registered, event will be delivered. -(See oom_control section) +When oom event notifier is registered, event will be delivered to the root +of the memory pressure which cannot be handled (See oom_control section) 2.6 Locking -- 2.0.0.rc0 -- 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/