From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f69.google.com (mail-lf0-f69.google.com [209.85.215.69]) by kanga.kvack.org (Postfix) with ESMTP id 98BC56B025F for ; Tue, 12 Jul 2016 04:33:46 -0400 (EDT) Received: by mail-lf0-f69.google.com with SMTP id g18so6228543lfg.2 for ; Tue, 12 Jul 2016 01:33:46 -0700 (PDT) Received: from outbound-smtp10.blacknight.com (outbound-smtp10.blacknight.com. [46.22.139.15]) by mx.google.com with ESMTPS id n3si3804715wjp.144.2016.07.12.01.33.45 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 12 Jul 2016 01:33:45 -0700 (PDT) Received: from mail.blacknight.com (pemlinmail01.blacknight.ie [81.17.254.10]) by outbound-smtp10.blacknight.com (Postfix) with ESMTPS id 795121C187B for ; Tue, 12 Jul 2016 09:33:44 +0100 (IST) Date: Tue, 12 Jul 2016 09:33:42 +0100 From: Mel Gorman Subject: Re: [PATCH] mm, vmscan: Give up balancing node for high order allocations earlier Message-ID: <20160712083342.GC9806@techsingularity.net> References: <00ed01d1d1c8$fcb12ff0$f6138fd0$@alibaba-inc.com> <20160711152015.e3be8be7702fb0ca4625040d@linux-foundation.org> <013d01d1dc07$33896860$9a9c3920$@alibaba-inc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <013d01d1dc07$33896860$9a9c3920$@alibaba-inc.com> Sender: owner-linux-mm@kvack.org List-ID: To: Hillf Danton Cc: 'Andrew Morton' , 'Johannes Weiner' , 'Vlastimil Babka' , 'linux-kernel' , linux-mm@kvack.org On Tue, Jul 12, 2016 at 02:32:45PM +0800, Hillf Danton wrote: > > > To avoid excessive reclaim, we give up rebalancing for high order > > > allocations right after reclaiming enough pages. > > > > hm. What are the observed runtime effects of this change? Any testing > > results? > > > This work was based on Mel's work, Sir, > "[PATCH 00/27] Move LRU page reclaim from zones to nodes v7". > I believe Andrew understands that but the question is what is the observed runtime effect of the patch? > In "[PATCH 06/27] mm, vmscan: Make kswapd reclaim in terms of nodes", > fragmentation detection is introduced to avoid excessive reclaim. We bail > out of balancing for high-order allocations if the pages reclaimed at the > __current__ reclaim priority are two times more than required. > > In this work we give up reclaiming for high-order allocations if the > __total__ number of pages reclaimed, from the first priority to the > current priority, is more than needed, and in net result we reclaim less > pages. > While it's clear what it does, it is not clear if it is an improvement. I had read the patch, considered merging it and decided against it. This decision was based on the fact the series did not appear to be over-reclaiming for high-order pages when compared with zone-lru. Did you test this patch with a workload that requires a lot of high-order pages and see if kswapd was over-reclaiming and that this patch addressed the issue? -- Mel Gorman SUSE Labs -- 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