Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932237Ab2JOWH2 (ORCPT ); Mon, 15 Oct 2012 18:07:28 -0400 Received: from cantor2.suse.de ([195.135.220.15]:58661 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932079Ab2JOWH1 (ORCPT ); Mon, 15 Oct 2012 18:07:27 -0400 Date: Tue, 16 Oct 2012 00:07:25 +0200 From: Michal Hocko To: Andrew Morton Cc: linux-mm@kvack.org, David Rientjes , KOSAKI Motohiro , KAMEZAWA Hiroyuki , Johannes Weiner , LKML Subject: [PATCH] doc: describe memcg swappiness more precisely memory.swappiness==0 Message-ID: <20121015220725.GB11682@dhcp22.suse.cz> References: <20121011085038.GA29295@dhcp22.suse.cz> <1349945859-1350-1-git-send-email-mhocko@suse.cz> <20121015220354.GA11682@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121015220354.GA11682@dhcp22.suse.cz> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1743 Lines: 46 And a follow up for memcg.swappiness documentation which is more specific about spwappiness==0 meaning. --- >From 1bc3a94fea728107ed108edd42df464b908cd067 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Mon, 15 Oct 2012 11:43:56 +0200 Subject: [PATCH] doc: describe memcg swappiness more precisely since fe35004f (mm: avoid swapping out with swappiness==0) memcg reclaim stopped swapping out anon pages completely when 0 value is used. Although this is somehow expected it hasn't been done for a really long time this way and so it is probably better to be explicit about the effect. Moreover global reclaim swapps out even when swappiness is 0 to prevent from OOM killer. Signed-off-by: Michal Hocko --- Documentation/cgroups/memory.txt | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt index c07f7b4..71c4da4 100644 --- a/Documentation/cgroups/memory.txt +++ b/Documentation/cgroups/memory.txt @@ -466,6 +466,10 @@ Note: 5.3 swappiness Similar to /proc/sys/vm/swappiness, but affecting a hierarchy of groups only. +Please note that unlike the global swappiness, memcg knob set to 0 +really prevents from any swapping even if there is a swap storage +available. This might lead to memcg OOM killer if there are no file +pages to reclaim. Following cgroups' swappiness can't be changed. - root cgroup (uses /proc/sys/vm/swappiness). -- 1.7.10.4 -- Michal Hocko SUSE Labs -- 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/