From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754991Ab3GDN3o (ORCPT ); Thu, 4 Jul 2013 09:29:44 -0400 Received: from cantor2.suse.de ([195.135.220.15]:46905 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752082Ab3GDN3n (ORCPT ); Thu, 4 Jul 2013 09:29:43 -0400 Date: Thu, 4 Jul 2013 14:29:39 +0100 From: Mel Gorman To: Srikar Dronamraju Cc: Peter Zijlstra , Ingo Molnar , Andrea Arcangeli , Johannes Weiner , Linux-MM , LKML Subject: Re: [PATCH 06/13] sched: Reschedule task on preferred NUMA node once selected Message-ID: <20130704132939.GQ1875@suse.de> References: <1372861300-9973-1-git-send-email-mgorman@suse.de> <1372861300-9973-7-git-send-email-mgorman@suse.de> <20130704122644.GA29916@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20130704122644.GA29916@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 05:56:44PM +0530, Srikar Dronamraju wrote: > * Mel Gorman [2013-07-03 15:21:33]: > > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > index 2a0bbc2..b9139be 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -800,6 +800,37 @@ unsigned int sysctl_numa_balancing_scan_delay = 1000; > > */ > > unsigned int sysctl_numa_balancing_settle_count __read_mostly = 3; > > > > +static unsigned long weighted_cpuload(const int cpu); > > + > > +static int > > +find_idlest_cpu_node(int this_cpu, int nid) > > +{ > > + unsigned long load, min_load = ULONG_MAX; > > + int i, idlest_cpu = this_cpu; > > + > > + BUG_ON(cpu_to_node(this_cpu) == nid); > > + > > + for_each_cpu(i, cpumask_of_node(nid)) { > > + load = weighted_cpuload(i); > > + > > + if (load < min_load) { > > + struct task_struct *p; > > + > > + /* Do not preempt a task running on its preferred node */ > > + struct rq *rq = cpu_rq(i); > > + raw_spin_lock_irq(&rq->lock); > > Not sure why we need this spin_lock? Cant this be done in a rcu block > instead? > Judging by how find_idlest_cpu works it would appear you are correct. Thanks very much, I'm still pretty much a scheduler wuss. I know what I want but not always how to get it :) -- Mel Gorman SUSE Labs