From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f198.google.com (mail-io0-f198.google.com [209.85.223.198]) by kanga.kvack.org (Postfix) with ESMTP id 9D9B06B0253 for ; Mon, 23 May 2016 06:38:12 -0400 (EDT) Received: by mail-io0-f198.google.com with SMTP id 82so154297723ior.0 for ; Mon, 23 May 2016 03:38:12 -0700 (PDT) Received: from EUR01-DB5-obe.outbound.protection.outlook.com (mail-db5eur01on0136.outbound.protection.outlook.com. [104.47.2.136]) by mx.google.com with ESMTPS id ea9si14503454oeb.37.2016.05.23.03.38.09 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 23 May 2016 03:38:10 -0700 (PDT) Date: Mon, 23 May 2016 13:37:58 +0300 From: Vladimir Davydov Subject: Re: [PATCH] mm: memcontrol: fix the return in mem_cgroup_margin Message-ID: <20160523103758.GB7917@esperanza> References: <1463556255-31892-1-git-send-email-roy.qing.li@gmail.com> <20160518073253.GC21654@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Li RongQing Cc: Michal Hocko , cgroups@vger.kernel.org, linux-mm@kvack.org, Johannes Weiner On Thu, May 19, 2016 at 09:44:53AM +0800, Li RongQing wrote: > On Wed, May 18, 2016 at 3:32 PM, Michal Hocko wrote: > > count should always be smaller than memsw.limit (this is a hard limit). > > Even if we have some temporary breach then the code should work as > > expected because margin is initialized to 0 and memsw.limit >= limit. > > is it possible for this case? for example > > memory count is 500, memory limit is 600; the margin is set to 100 firstly, > then check memory+swap limit, its count(1100) is bigger than its limit(1000), > then the margin 100 is returned wrongly. I guess it is possible, because try_charge forces charging __GFP_NOFAIL allocations, which may result in memsw.limit excess. If we are below memory.limit and there's nothing to reclaim to reduce memsw.usage, we might end up looping in try_charge forever. I've never seen that happen in practice, but I still think the patch is worth applying. Acked-by: Vladimir Davydov -- 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