From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757291Ab3GEKHq (ORCPT ); Fri, 5 Jul 2013 06:07:46 -0400 Received: from cantor2.suse.de ([195.135.220.15]:49474 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757206Ab3GEKHp (ORCPT ); Fri, 5 Jul 2013 06:07:45 -0400 Date: Fri, 5 Jul 2013 11:07:41 +0100 From: Mel Gorman To: Srikar Dronamraju Cc: Peter Zijlstra , Ingo Molnar , Andrea Arcangeli , Johannes Weiner , Linux-MM , LKML Subject: Re: [PATCH 11/13] sched: Check current->mm before allocating NUMA faults Message-ID: <20130705100741.GV1875@suse.de> References: <1372861300-9973-1-git-send-email-mgorman@suse.de> <1372861300-9973-12-git-send-email-mgorman@suse.de> <20130704124823.GB29916@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20130704124823.GB29916@linux.vnet.ibm.com> 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 Thu, Jul 04, 2013 at 06:18:23PM +0530, Srikar Dronamraju wrote: > * Mel Gorman [2013-07-03 15:21:38]: > > > task_numa_placement checks current->mm but after buffers for faults > > have already been uselessly allocated. Move the check earlier. > > > > [peterz@infradead.org: Identified the problem] > > Signed-off-by: Mel Gorman > > --- > > kernel/sched/fair.c | 22 ++++++++++++++-------- > > 1 file changed, 14 insertions(+), 8 deletions(-) > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > index 336074f..3c796b0 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -870,8 +870,6 @@ static void task_numa_placement(struct task_struct *p) > > int seq, nid, max_nid = 0; > > unsigned long max_faults = 0; > > > > - if (!p->mm) /* for example, ksmd faulting in a user's mm */ > > - return; > > seq = ACCESS_ONCE(p->mm->numa_scan_seq); > > if (p->numa_scan_seq == seq) > > return; > > @@ -945,6 +943,12 @@ void task_numa_fault(int last_nid, int node, int pages, bool migrated) > > if (!sched_feat_numa(NUMA)) > > return; > > > > + /* for example, ksmd faulting in a user's mm */ > > + if (!p->mm) { > > + p->numa_scan_period = sysctl_numa_balancing_scan_period_max; > > Naive question: > Why are we resetting the scan_period? > At the time I wrote it I was thinking of tick times and meant to recheck if it's necessary but then it slipped my mind. The reset is unnecessary as curr->mm is already checked. -- Mel Gorman SUSE Labs