From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755959Ab3GKLYu (ORCPT ); Thu, 11 Jul 2013 07:24:50 -0400 Received: from merlin.infradead.org ([205.233.59.134]:41701 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755882Ab3GKLYt (ORCPT ); Thu, 11 Jul 2013 07:24:49 -0400 Date: Thu, 11 Jul 2013 13:23:59 +0200 From: Peter Zijlstra To: Mel Gorman Cc: Srikar Dronamraju , Ingo Molnar , Andrea Arcangeli , Johannes Weiner , Linux-MM , LKML Subject: Re: [PATCH 05/16] sched: Select a preferred node with the most numa hinting faults Message-ID: <20130711112359.GG25631@dyad.programming.kicks-ass.net> References: <1373536020-2799-1-git-send-email-mgorman@suse.de> <1373536020-2799-6-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1373536020-2799-6-git-send-email-mgorman@suse.de> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 11, 2013 at 10:46:49AM +0100, Mel Gorman wrote: > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -1593,6 +1593,7 @@ static void __sched_fork(struct task_struct *p) > p->numa_scan_seq = p->mm ? p->mm->numa_scan_seq : 0; > p->numa_migrate_seq = p->mm ? p->mm->numa_scan_seq - 1 : 0; > p->numa_scan_period = sysctl_numa_balancing_scan_delay; > + p->numa_preferred_nid = -1; (1) > p->numa_work.next = &p->numa_work; > p->numa_faults = NULL; > #endif /* CONFIG_NUMA_BALANCING */ > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 904fd6f..c0bee41 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -793,7 +793,8 @@ unsigned int sysctl_numa_balancing_scan_delay = 1000; > > static void task_numa_placement(struct task_struct *p) > { > - int seq; > + int seq, nid, max_nid = 0; Should you not start with max_nid = -1? > + unsigned long max_faults = 0; > > if (!p->mm) /* for example, ksmd faulting in a user's mm */ > return; > @@ -802,7 +803,19 @@ static void task_numa_placement(struct task_struct *p) > return; > p->numa_scan_seq = seq; > > - /* FIXME: Scheduling placement policy hints go here */ > + /* Find the node with the highest number of faults */ > + for (nid = 0; nid < nr_node_ids; nid++) { > + unsigned long faults = p->numa_faults[nid]; > + p->numa_faults[nid] >>= 1; > + if (faults > max_faults) { > + max_faults = faults; > + max_nid = nid; > + } > + } > + It is rather unlikely; but suppose the entire ->numa_faults[] array is 0, you'd somehow end up selecting max_nid := 0. Which seems inconsistent with \1. > + /* Update the tasks preferred node if necessary */ > + if (max_faults && max_nid != p->numa_preferred_nid) > + p->numa_preferred_nid = max_nid; > } > > /* > -- > 1.8.1.4 >