From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yk0-f181.google.com (mail-yk0-f181.google.com [209.85.160.181]) by kanga.kvack.org (Postfix) with ESMTP id 1D72E6B0253 for ; Fri, 28 Aug 2015 16:53:05 -0400 (EDT) Received: by ykba134 with SMTP id a134so14681062ykb.1 for ; Fri, 28 Aug 2015 13:53:04 -0700 (PDT) Received: from mail-yk0-x22f.google.com (mail-yk0-x22f.google.com. [2607:f8b0:4002:c07::22f]) by mx.google.com with ESMTPS id e185si3254049ywc.4.2015.08.28.13.53.04 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 28 Aug 2015 13:53:04 -0700 (PDT) Received: by ykdz80 with SMTP id z80so27643447ykd.0 for ; Fri, 28 Aug 2015 13:53:04 -0700 (PDT) Date: Fri, 28 Aug 2015 16:53:01 -0400 From: Tejun Heo Subject: Re: [PATCH 3/4] memcg: punt high overage reclaim to return-to-userland path Message-ID: <20150828205301.GB11089@htj.dyndns.org> References: <1440775530-18630-1-git-send-email-tj@kernel.org> <1440775530-18630-4-git-send-email-tj@kernel.org> <20150828171322.GC21463@dhcp22.suse.cz> <20150828204554.GM9610@esperanza> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150828204554.GM9610@esperanza> Sender: owner-linux-mm@kvack.org List-ID: To: Vladimir Davydov Cc: Michal Hocko , hannes@cmpxchg.org, cgroups@vger.kernel.org, linux-mm@kvack.org, kernel-team@fb.com Hello, Vladmir. On Fri, Aug 28, 2015 at 11:45:54PM +0300, Vladimir Davydov wrote: > Actually, memory.high by itself *is* the protection against GFP_NOWAIT > allocations, similarly to zone watermarks. W/o it we would have no other > choice but fail a GFP_NOWAIT allocation on hitting memory.max. One > should just set it so that > > memory.max - memory.high > [max sum size of !__GFP_WAIT allocations > that can normally occur in a row] While this would be true in many cases, I don't think this is the intention of the two knobs and the space between high and max can be filled up by anything which can't be reclaimed - e.g. too many dirty / writeback pages on a slow device or memlocked pages. If it were really the buffer for GFP_NOWAIT, there's no reason to even make it a separate knob and we *may* change how over-high reclaim behaves in the future, so let's please not dig ourselves into something too specific. > That being said, currently I don't see any point in making memory.high > !__GFP_WAIT-safe. Yeah, as long as the blow up can't be triggered consistently, it should be fine. Thanks. -- tejun -- 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