From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756365AbcGGK6P (ORCPT ); Thu, 7 Jul 2016 06:58:15 -0400 Received: from outbound-smtp07.blacknight.com ([46.22.139.12]:39583 "EHLO outbound-smtp07.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751618AbcGGK6O (ORCPT ); Thu, 7 Jul 2016 06:58:14 -0400 Date: Thu, 7 Jul 2016 11:58:09 +0100 From: Mel Gorman To: Joonsoo Kim Cc: Andrew Morton , Linux-MM , Rik van Riel , Vlastimil Babka , Johannes Weiner , LKML Subject: Re: [PATCH 20/31] mm, vmscan: only wakeup kswapd once per node for the requested classzone Message-ID: <20160707105809.GU11498@techsingularity.net> References: <1467403299-25786-1-git-send-email-mgorman@techsingularity.net> <1467403299-25786-21-git-send-email-mgorman@techsingularity.net> <20160707012423.GC27987@js1304-P5Q-DELUXE> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20160707012423.GC27987@js1304-P5Q-DELUXE> 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 Thu, Jul 07, 2016 at 10:24:23AM +0900, Joonsoo Kim wrote: > On Fri, Jul 01, 2016 at 09:01:28PM +0100, Mel Gorman wrote: > > kswapd is woken when zones are below the low watermark but the wakeup > > decision is not taking the classzone into account. Now that reclaim is > > node-based, it is only required to wake kswapd once per node and only if > > all zones are unbalanced for the requested classzone. > > > > Note that one node might be checked multiple times if the zonelist is > > ordered by node because there is no cheap way of tracking what nodes have > > already been visited. For zone-ordering, each node should be checked only > > once. > > > > Signed-off-by: Mel Gorman > > Acked-by: Vlastimil Babka > > --- > > mm/page_alloc.c | 8 ++++++-- > > mm/vmscan.c | 13 +++++++++++-- > > 2 files changed, 17 insertions(+), 4 deletions(-) > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index 441f482bf9a2..2fe2fbb4f2ad 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -3410,10 +3410,14 @@ static void wake_all_kswapds(unsigned int order, const struct alloc_context *ac) > > { > > struct zoneref *z; > > struct zone *zone; > > + pg_data_t *last_pgdat = NULL; > > > > for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, > > - ac->high_zoneidx, ac->nodemask) > > - wakeup_kswapd(zone, order, ac_classzone_idx(ac)); > > + ac->high_zoneidx, ac->nodemask) { > > + if (last_pgdat != zone->zone_pgdat) > > + wakeup_kswapd(zone, order, ac_classzone_idx(ac)); > > + last_pgdat = zone->zone_pgdat; > > + } > > } > > In wakeup_kswapd(), there is a check if it is a populated zone or not. It's redundant. > If first zone in node is not a populated zone, wakeup_kswapd() would be > skipped. Though, I'm not sure if zonelist can include a un-populated > zone. Zonelists do not contain unpopulated zones. > Perhaps, moving populated zone check in wakeup_kswapd() to here > would be a safe code. > If anything was going to happen to it, it should be deleted. It's a minor cleanup. -- Mel Gorman SUSE Labs