From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f71.google.com (mail-wm0-f71.google.com [74.125.82.71]) by kanga.kvack.org (Postfix) with ESMTP id 021E56B026C for ; Thu, 18 Aug 2016 05:44:05 -0400 (EDT) Received: by mail-wm0-f71.google.com with SMTP id o80so12433728wme.1 for ; Thu, 18 Aug 2016 02:44:04 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id yt2si1079139wjb.283.2016.08.18.02.44.03 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 18 Aug 2016 02:44:03 -0700 (PDT) Subject: Re: [PATCH v6 06/11] mm, compaction: more reliably increase direct compaction priority References: <20160810091226.6709-1-vbabka@suse.cz> <20160810091226.6709-7-vbabka@suse.cz> <20160818091036.GF30162@dhcp22.suse.cz> From: Vlastimil Babka Message-ID: <1f761527-ed12-ba16-0565-c64d14e200eb@suse.cz> Date: Thu, 18 Aug 2016 11:44:00 +0200 MIME-Version: 1.0 In-Reply-To: <20160818091036.GF30162@dhcp22.suse.cz> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Andrew Morton , Mel Gorman , Joonsoo Kim , David Rientjes , Rik van Riel , linux-mm@kvack.org, linux-kernel@vger.kernel.org On 08/18/2016 11:10 AM, Michal Hocko wrote: > On Wed 10-08-16 11:12:21, Vlastimil Babka wrote: >> During reclaim/compaction loop, compaction priority can be increased by the >> should_compact_retry() function, but the current code is not optimal. Priority >> is only increased when compaction_failed() is true, which means that compaction >> has scanned the whole zone. This may not happen even after multiple attempts >> with a lower priority due to parallel activity, so we might needlessly >> struggle on the lower priorities and possibly run out of compaction retry >> attempts in the process. >> >> After this patch we are guaranteed at least one attempt at the highest >> compaction priority even if we exhaust all retries at the lower priorities. > > I expect we will tend to do some special handling at the highest > priority so guaranteeing at least one run with that prio seems sensible to me. The only > question is whether we really want to enforce the highest priority for > costly orders as well. I think we want to reserve the highest (maybe add > one more) prio for !costly orders as those invoke the OOM killer and the > failure are quite disruptive. Costly orders are already ruled out of reaching the highest priority unless they are __GFP_REPEAT, so I assumed that if they are allocations with __GFP_REPEAT, they really would like to succeed, so let them use the highest priority. -- 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