From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933507AbcGGBVA (ORCPT ); Wed, 6 Jul 2016 21:21:00 -0400 Received: from LGEAMRELO12.lge.com ([156.147.23.52]:46599 "EHLO lgeamrelo12.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933452AbcGGBU6 (ORCPT ); Wed, 6 Jul 2016 21:20:58 -0400 X-Original-SENDERIP: 156.147.1.121 X-Original-MAILFROM: iamjoonsoo.kim@lge.com X-Original-SENDERIP: 10.177.222.138 X-Original-MAILFROM: iamjoonsoo.kim@lge.com Date: Thu, 7 Jul 2016 10:24:23 +0900 From: Joonsoo Kim To: Mel Gorman 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: <20160707012423.GC27987@js1304-P5Q-DELUXE> References: <1467403299-25786-1-git-send-email-mgorman@techsingularity.net> <1467403299-25786-21-git-send-email-mgorman@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1467403299-25786-21-git-send-email-mgorman@techsingularity.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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. Perhaps, moving populated zone check in wakeup_kswapd() to here would be a safe code. Thanks. > > static inline unsigned int > diff --git a/mm/vmscan.c b/mm/vmscan.c > index c1c8b77d8cb4..e02091be0e12 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -3420,6 +3420,7 @@ 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; > @@ -3433,8 +3434,16 @@ 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); > -- > 2.6.4 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: email@kvack.org