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From: Peter Zijlstra <peterz@infradead.org>
To: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: Abysmal scheduler performance in Linus' tree?
Date: Wed, 6 Sep 2017 12:44:20 +0200
Message-ID: <20170906104420.ic5lbpacpyyz53w5@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <150469312649.28581.17626550155735691534@mail.alporthouse.com>

On Wed, Sep 06, 2017 at 11:18:46AM +0100, Chris Wilson wrote:

> > +static void get_llc_stats(struct llc_stats *stats, int cpu)
> > +{
> > +       struct sched_domain_shared *sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
> > +
> > +       if (!sds) {
> > +               memset(&stats, 0, sizeof(*stats));
> 
> Yes, I even sent you a mail about it ;)

Bah, too much email, sorry :-(

> > +       /*
> > +        * The has_capacity stuff is not SMT aware, but by trying to balance
> > +        * the nr_running on both ends we try and fill the domain at equal
> > +        * rates, thereby first consuming cores before siblings.
> > +        */
> > +
> > +       /* if the old cache has capacity, stay there */
> > +       if (prev_stats.has_capacity && prev_stats.nr_running < this_stats.nr_running+1)
> > +               return false;
> > +
> > +       /* if this cache has capacity, come here */
> > +       if (this_stats.has_capacity && this_stats.nr_running < prev_stats.nr_running+1)
> > +               return true;
> 
> This is still not working as intended, it should be 
> 
> 	if (this_stats.has_capacity && this_stats.nr_running+1 < prev_stats.nr_running)
> 		return true;
> 
> to fix the regression.

Argh, you're quite right. Let me do a patch for that.

  parent reply index

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-06  5:13 Andy Lutomirski
2017-09-06  8:25 ` Peter Zijlstra
2017-09-06  8:59   ` Andy Lutomirski
2017-09-06  9:03     ` Peter Zijlstra
2017-09-06 16:14       ` Peter Zijlstra
2017-09-07  6:15         ` Mike Galbraith
2017-09-07  7:31           ` Ingo Molnar
2017-09-07  9:13           ` [PATCH] sched/cpuset/pm: Fix cpuset vs suspend-resume Peter Zijlstra
2017-09-07  9:26             ` Peter Zijlstra
2017-09-07 10:54               ` Rafael J. Wysocki
2017-09-07 20:38               ` Tejun Heo
2017-09-07 10:33             ` [tip:sched/urgent] sched/cpuset/pm: Fix cpuset vs. suspend-resume bugs tip-bot for Peter Zijlstra
2017-09-06  9:15 ` Abysmal scheduler performance in Linus' tree? Chris Wilson
2017-09-06  9:24   ` Peter Zijlstra
     [not found]     ` <150469312649.28581.17626550155735691534@mail.alporthouse.com>
2017-09-06 10:44       ` Peter Zijlstra [this message]
2017-09-06 10:51         ` Peter Zijlstra
2017-09-07  8:16           ` [tip:sched/urgent] sched/fair: Fix wake_affine_llc() balancing rules tip-bot for Peter Zijlstra

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