linux-kernel - Re: [PATCH 4/4] sched/fair: Do not migrate due to a sync wakeup on exit

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Message-ID: <20180212200938.sfofuhztrsbvsriy@techsingularity.net>
Date:   Mon, 12 Feb 2018 20:09:38 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Andreas Mohr <andi@...as.de>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Mike Galbraith <efault@....de>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] sched/fair: Do not migrate due to a sync wakeup on
 exit

On Mon, Feb 12, 2018 at 09:01:27PM +0100, Andreas Mohr wrote:
> Hello,
> 
> On Mon, Feb 12, 2018 at 02:58:57PM +0000, Mel Gorman wrote:
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 28c8d9c91955..50442697b455 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -5710,8 +5710,14 @@ wake_affine_idle(int this_cpu, int prev_cpu, int sync)
> >  	if (idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
> >  		return idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
> >  
> > -	if (sync && cpu_rq(this_cpu)->nr_running == 1)
> > +	if (sync && cpu_rq(this_cpu)->nr_running == 1) {
> > +		/* Avoid tasks exiting pulling parents to new nodes */
> 
> Semi-confusing wording (WTH are "pulling parents"? :) - possibly better variant?:
> Avoid having exiting tasks pull their parents to new nodes

That is better wording. If I don't replace the patch with Peter's
version, I'll update it.

> Good catch, it seems.
> 

Thanks.

-- 
Mel Gorman
SUSE Labs