From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758583AbcH3MHg (ORCPT ); Tue, 30 Aug 2016 08:07:36 -0400 Received: from outbound-smtp06.blacknight.com ([81.17.249.39]:36724 "EHLO outbound-smtp06.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758241AbcH3MHc (ORCPT ); Tue, 30 Aug 2016 08:07:32 -0400 Date: Tue, 30 Aug 2016 13:07:28 +0100 From: Mel Gorman To: Srikar Dronamraju Cc: Andrew Morton , Linux-MM , Rik van Riel , Vlastimil Babka , Johannes Weiner , Minchan Kim , Joonsoo Kim , LKML , Michael Ellerman , linuxppc-dev@lists.ozlabs.org, Mahesh Salgaonkar , Hari Bathini Subject: Re: [PATCH 07/34] mm, vmscan: make kswapd reclaim in terms of nodes Message-ID: <20160830120728.GV8119@techsingularity.net> References: <1467970510-21195-1-git-send-email-mgorman@techsingularity.net> <1467970510-21195-8-git-send-email-mgorman@techsingularity.net> <20160829093844.GA2592@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20160829093844.GA2592@linux.vnet.ibm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 29, 2016 at 03:08:44PM +0530, Srikar Dronamraju wrote: > > Patch "mm: vmscan: Begin reclaiming pages on a per-node basis" started > > thinking of reclaim in terms of nodes but kswapd is still zone-centric. This > > patch gets rid of many of the node-based versus zone-based decisions. > > > > o A node is considered balanced when any eligible lower zone is balanced. > > This eliminates one class of age-inversion problem because we avoid > > reclaiming a newer page just because it's in the wrong zone > > o pgdat_balanced disappears because we now only care about one zone being > > balanced. > > o Some anomalies related to writeback and congestion tracking being based on > > zones disappear. > > o kswapd no longer has to take care to reclaim zones in the reverse order > > that the page allocator uses. > > o Most importantly of all, reclaim from node 0 with multiple zones will > > have similar aging and reclaiming characteristics as every > > other node. > > > > Signed-off-by: Mel Gorman > > Acked-by: Johannes Weiner > > Acked-by: Vlastimil Babka > > This patch seems to hurt FA_DUMP functionality. This behaviour is not > seen on v4.7 but only after this patch. > > So when a kernel on a multinode machine with memblock_reserve() such > that most of the nodes have zero available memory, kswapd seems to be > consuming 100% of the time. > Why is FA_DUMP specifically the trigger? If the nodes have zero available memory then is the zone_populated() check failing when FA_DUMP is enabled? If so, that would both allow kswapd to wake and stay awake. -- Mel Gorman SUSE Labs