linux-kernel - Re: [PATCH 2/2] sched/numa: Delay retrying placement for automatic NUMA balance after wake

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Message-ID: <20180212181104.ynmpzlexuksn5oi6@techsingularity.net>
Date:   Mon, 12 Feb 2018 18:11:04 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Mike Galbraith <efault@....de>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] sched/numa: Delay retrying placement for automatic
 NUMA balance after wake_affine

On Mon, Feb 12, 2018 at 06:37:43PM +0100, Peter Zijlstra wrote:
> On Mon, Feb 12, 2018 at 05:11:31PM +0000, Mel Gorman wrote:
> > +static void
> > +update_wa_numa_placement(struct task_struct *p, int prev_cpu, int target)
> > +{
> > +	unsigned long interval;
> > +
> > +	if (!static_branch_likely(&sched_numa_balancing))
> > +		return;
> > +
> > +	/* If balancing has no preference then accept the target */
> > +	if (p->numa_preferred_nid == -1)
> > +		return;
> > +
> > +	/* If the wakeup is not affecting locality then accept the target */
> > +	if (cpus_share_cache(prev_cpu, target))
> > +		return;
> 
> Both the above comments speak of 'accepting' the target, but its a void
> function, there's nothing they can do about it. It cannot not accept the
> placement.
> 

It's stale phrasing from an initial prototype that tried altering the
placement which failed miserably. I'll fix it.

-- 
Mel Gorman
SUSE Labs