From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753015AbcGFIb2 (ORCPT ); Wed, 6 Jul 2016 04:31:28 -0400 Received: from outbound-smtp11.blacknight.com ([46.22.139.16]:34621 "EHLO outbound-smtp11.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750779AbcGFIbZ (ORCPT ); Wed, 6 Jul 2016 04:31:25 -0400 Date: Wed, 6 Jul 2016 09:31:21 +0100 From: Mel Gorman To: Minchan Kim Cc: Andrew Morton , Linux-MM , Rik van Riel , Vlastimil Babka , Johannes Weiner , LKML Subject: Re: [PATCH 08/31] mm, vmscan: simplify the logic deciding whether kswapd sleeps Message-ID: <20160706083121.GL11498@techsingularity.net> References: <1467403299-25786-1-git-send-email-mgorman@techsingularity.net> <1467403299-25786-9-git-send-email-mgorman@techsingularity.net> <20160705055931.GC28164@bbox> <20160705102639.GG11498@techsingularity.net> <20160706003054.GC12570@bbox> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20160706003054.GC12570@bbox> 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 Wed, Jul 06, 2016 at 09:30:54AM +0900, Minchan Kim wrote: > On Tue, Jul 05, 2016 at 11:26:39AM +0100, Mel Gorman wrote: > > > > > > > @@ -3418,10 +3426,10 @@ void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) > > > > if (!cpuset_zone_allowed(zone, GFP_KERNEL | __GFP_HARDWALL)) > > > > return; > > > > pgdat = zone->zone_pgdat; > > > > - if (pgdat->kswapd_max_order < order) { > > > > - pgdat->kswapd_max_order = order; > > > > - pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx); > > > > - } > > > > + if (pgdat->kswapd_classzone_idx == -1) > > > > + pgdat->kswapd_classzone_idx = classzone_idx; > > > > > > It's tricky. Couldn't we change kswapd_classzone_idx to integer type > > > and remove if above if condition? > > > > > > > It's tricky and not necessarily better overall. It's perfectly possible > > to be woken up for zone index 0 so it's changing -1 to another magic > > value. > > I don't get it. What is a problem with this? > It becomes difficult to tell the difference between "no wakeup and init to zone 0" and "wakeup and reclaim for zone 0". At least that's the problem I ran into when I tried before settling on -1. -- Mel Gorman SUSE Labs