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Subject: Re: CFS Bandwidth Control - Test results of cgroups tasks pinned vs
 unpinnede
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Paul Turner <pjt@google.com>,
        Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>,
        Vladimir Davydov <vdavydov@parallels.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Bharata B Rao <bharata@linux.vnet.ibm.com>,
        Dhaval Giani <dhaval.giani@gmail.com>,
        Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>,
        Ingo Molnar <mingo@elte.hu>, Pavel Emelianov <xemul@parallels.com>,
        Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 13 Sep 2011 16:19:39 +0200
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On Tue, 2011-09-13 at 09:45 +0530, Srivatsa Vaddagiri wrote:
> * Peter Zijlstra <a.p.zijlstra@chello.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.