From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755166AbcFQKqK (ORCPT ); Fri, 17 Jun 2016 06:46:10 -0400 Received: from mx2.suse.de ([195.135.220.15]:48211 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751757AbcFQKqI (ORCPT ); Fri, 17 Jun 2016 06:46:08 -0400 Subject: Re: [PATCH 21/27] mm, vmscan: Only wakeup kswapd once per node for the requested classzone To: Mel Gorman , Andrew Morton , Linux-MM References: <1465495483-11855-1-git-send-email-mgorman@techsingularity.net> <1465495483-11855-22-git-send-email-mgorman@techsingularity.net> Cc: Rik van Riel , Johannes Weiner , LKML From: Vlastimil Babka Message-ID: <2ce07fcf-7b7d-a70b-ed7b-60867ad4458f@suse.cz> Date: Fri, 17 Jun 2016 12:46:05 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.0 MIME-Version: 1.0 In-Reply-To: <1465495483-11855-22-git-send-email-mgorman@techsingularity.net> Content-Type: text/plain; charset=iso-8859-2; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/09/2016 08:04 PM, 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 but there is no cheap > way of tracking what nodes have already been visited for zoneslists that > be ordered by either zone or node. Wouldn't it be possible to optimize for node order as you did in direct reclaim? Do the zone_balanced checks when going through zonelist, and once node changes in iteration, wake up if no eligible zones visited so far were balanced. > Signed-off-by: Mel Gorman > --- > mm/vmscan.c | 13 +++++++++++-- > 1 file changed, 11 insertions(+), 2 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 7a2d69612231..b9cff9047ac0 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -3389,6 +3389,7 @@ static int kswapd(void *p) > void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) > { > pg_data_t *pgdat; > + int z; > > if (!populated_zone(zone)) > return; > @@ -3402,8 +3403,16 @@ void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) > pgdat->kswapd_order = max(pgdat->kswapd_order, order); > if (!waitqueue_active(&pgdat->kswapd_wait)) > return; > - if (zone_balanced(zone, order, 0)) > - return; > + > + /* Only wake kswapd if all zones are unbalanced */ > + for (z = 0; z <= classzone_idx; z++) { > + zone = pgdat->node_zones + z; > + if (!populated_zone(zone)) > + continue; > + > + if (zone_balanced(zone, order, classzone_idx)) > + return; > + } > > trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order); > wake_up_interruptible(&pgdat->kswapd_wait); >