From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752866AbcGMIlI (ORCPT ); Wed, 13 Jul 2016 04:41:08 -0400 Received: from outbound-smtp11.blacknight.com ([46.22.139.16]:55769 "EHLO outbound-smtp11.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751436AbcGMIlA (ORCPT ); Wed, 13 Jul 2016 04:41:00 -0400 Date: Wed, 13 Jul 2016 09:40:37 +0100 From: Mel Gorman To: Johannes Weiner Cc: Andrew Morton , Linux-MM , Rik van Riel , Vlastimil Babka , Minchan Kim , Joonsoo Kim , LKML Subject: Re: [PATCH 11/34] mm, vmscan: remove duplicate logic clearing node congestion and dirty state Message-ID: <20160713084037.GF9806@techsingularity.net> References: <1467970510-21195-1-git-send-email-mgorman@techsingularity.net> <1467970510-21195-12-git-send-email-mgorman@techsingularity.net> <20160712142256.GE5881@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20160712142256.GE5881@cmpxchg.org> 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 Tue, Jul 12, 2016 at 10:22:56AM -0400, Johannes Weiner wrote: > On Fri, Jul 08, 2016 at 10:34:47AM +0100, Mel Gorman wrote: > > @@ -3008,7 +3008,17 @@ static bool zone_balanced(struct zone *zone, int order, int classzone_idx) > > { > > unsigned long mark = high_wmark_pages(zone); > > > > - return zone_watermark_ok_safe(zone, order, mark, classzone_idx); > > + if (!zone_watermark_ok_safe(zone, order, mark, classzone_idx)) > > + return false; > > + > > + /* > > + * If any eligible zone is balanced then the node is not considered > > + * to be congested or dirty > > + */ > > + clear_bit(PGDAT_CONGESTED, &zone->zone_pgdat->flags); > > + clear_bit(PGDAT_DIRTY, &zone->zone_pgdat->flags); > > Predicate functions that secretly modify internal state give me the > willies... The diffstat is flat, too. Is this really an improvement? Primarily, it's about less duplicated code and maintenance overhead. Overall I was both trying to remove side-effects and make the kswapd flow easier to follow. I'm open to renaming suggestions that make it clear the function has side-effects. Best I came up with after the first coffee is try_reset_zone_balanced() which returns true with congestion/dirty state cleared if the zone is balanced. The name is not great because it's also a little misleading. It doesn't try to reset anything, that's reclaim's job. -- Mel Gorman SUSE Labs