linux-kernel - Re: [PATCH 3/4] sched: introduce synchronized idle injection

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Message-ID: <20151123180706.GN17308@twins.programming.kicks-ass.net>
Date:	Mon, 23 Nov 2015 19:07:06 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Javi Merino <javi.merino@....com>
Cc:	Jacob Pan <jacob.jun.pan@...ux.intel.com>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	John Stultz <john.stultz@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Len Brown <len.brown@...el.com>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>,
	Eduardo Valentin <edubezval@...il.com>,
	Paul Turner <pjt@...gle.com>,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	Juri Lelli <Juri.Lelli@....com>
Subject: Re: [PATCH 3/4] sched: introduce synchronized idle injection

On Mon, Nov 23, 2015 at 05:56:44PM +0000, Javi Merino wrote:
> I've tested this series on Juno (2xCortex-A57 4xCortex-A53).  If you
> idle inject for 50% of the time, when I run 6 busy loops the scheduler
> sometimes keeps two of them in the same cpu while the another cpu is
> completely idle.  Without idle injection the scheduler does the
> sensible thing: put one busy loop in each CPU.  I'm running systemd
> and this only happens with CONFIG_SCHED_AUTOGROUP=y.  If I unset
> CONFIG_SCHED_AUTOGROUP, the tasks are spread across all cpus as usual.

That's not a plus for this patch though; but a bug report against
AUTOGROUP/cgroup muck, right?
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