From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754812AbcGEION (ORCPT ); Tue, 5 Jul 2016 04:14:13 -0400 Received: from outbound-smtp10.blacknight.com ([46.22.139.15]:42043 "EHLO outbound-smtp10.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751460AbcGEIOJ (ORCPT ); Tue, 5 Jul 2016 04:14:09 -0400 Date: Tue, 5 Jul 2016 09:14:05 +0100 From: Mel Gorman To: Minchan Kim Cc: Andrew Morton , Linux-MM , Rik van Riel , Vlastimil Babka , Johannes Weiner , LKML Subject: Re: [PATCH 01/31] mm, vmstat: add infrastructure for per-node vmstats Message-ID: <20160705081405.GE11498@techsingularity.net> References: <1467403299-25786-1-git-send-email-mgorman@techsingularity.net> <1467403299-25786-2-git-send-email-mgorman@techsingularity.net> <20160704235018.GA26749@bbox> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20160704235018.GA26749@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 Tue, Jul 05, 2016 at 08:50:18AM +0900, Minchan Kim wrote: > > @@ -172,13 +174,17 @@ void refresh_zone_stat_thresholds(void) > > int threshold; > > > > for_each_populated_zone(zone) { > > + struct pglist_data *pgdat = zone->zone_pgdat; > > unsigned long max_drift, tolerate_drift; > > > > threshold = calculate_normal_threshold(zone); > > > > - for_each_online_cpu(cpu) > > + for_each_online_cpu(cpu) { > > per_cpu_ptr(zone->pageset, cpu)->stat_threshold > > = threshold; > > + per_cpu_ptr(pgdat->per_cpu_nodestats, cpu)->stat_threshold > > + = threshold; > > + } > > I didn't see other patches yet so it might fix it then. > > per_cpu_nodestats is per node not zone but it use per-zone threshold > and even overwritten by next zones. I don't think it's not intended. It was intended that the threshold from one zone would be used but now that you point it out, it would use the threshold for the smallest zone in the node which is sub-optimal. I applied the patch below on top to use the threshold from the largest zone. I considered using the sum of all thresholds but feared it might allow too much per-cpu drift. It can be switched to the sum if we find a case where vmstat updates are too high. diff --git a/mm/vmstat.c b/mm/vmstat.c index 90b0737ee4be..3345d396a99b 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -169,10 +169,18 @@ int calculate_normal_threshold(struct zone *zone) */ void refresh_zone_stat_thresholds(void) { + struct pglist_data *pgdat; struct zone *zone; int cpu; int threshold; + /* Zero current pgdat thresholds */ + for_each_online_pgdat(pgdat) { + for_each_online_cpu(cpu) { + per_cpu_ptr(pgdat->per_cpu_nodestats, cpu)->stat_threshold = 0; + } + } + for_each_populated_zone(zone) { struct pglist_data *pgdat = zone->zone_pgdat; unsigned long max_drift, tolerate_drift; @@ -180,10 +188,15 @@ void refresh_zone_stat_thresholds(void) threshold = calculate_normal_threshold(zone); for_each_online_cpu(cpu) { + int pgdat_threshold; + per_cpu_ptr(zone->pageset, cpu)->stat_threshold = threshold; + + /* Base nodestat threshold on the largest populated zone. */ + pgdat_threshold = per_cpu_ptr(pgdat->per_cpu_nodestats, cpu)->stat_threshold; per_cpu_ptr(pgdat->per_cpu_nodestats, cpu)->stat_threshold - = threshold; + = max(threshold, pgdat_threshold); } /* -- Mel Gorman SUSE Labs