linux-kernel - Re: CFS Bandwidth Control - Test results of cgroups tasks pinned vs unpinnede

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Date:	Tue, 13 Sep 2011 16:19:39 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
Cc:	Paul Turner <pjt@...gle.com>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	Vladimir Davydov <vdavydov@...allels.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Bharata B Rao <bharata@...ux.vnet.ibm.com>,
	Dhaval Giani <dhaval.giani@...il.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Pavel Emelianov <xemul@...allels.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: CFS Bandwidth Control - Test results of cgroups tasks pinned vs
 unpinnede

On Tue, 2011-09-13 at 09:45 +0530, Srivatsa Vaddagiri wrote:
> * Peter Zijlstra <a.p.zijlstra@...llo.nl> [2011-09-12 14:35:43]:
> 
> > Of course it does.. and I bet you can improve that slightly if you
> > manage to fix some of the numerical nightmares that live in the cgroup
> > load-balancer (Paul, care to share your WIP?)
> 
> Booting with "nohz=off" also helps significantly.
> 
> With nohz=on, average idle time (over 1 min) is 10.3%
> With nohz=off, average idle time (over 1 min) is 3.9%

So we should put the cpufreq/idle governor into the nohz/idle path, it
already tries to predict the idle duration in order to pick a C state,
that same prediction should be used to determine if stopping the tick is
worth it.

This has come up previously, but I can't quite recollect in what
context.
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