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Subject: Re: CFS Bandwidth Control - Test results of cgroups tasks pinned vs
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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>,
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        "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>
Date: Tue, 13 Sep 2011 20:07:41 +0200
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On Tue, 2011-09-13 at 23:24 +0530, Srivatsa Vaddagiri wrote:
> I guess the additional "system" time
> can't be accounted for easily by the tick-based accounting system we
> have. I agree there could be other un-observed side-effects of increased
> load-balance frequency (like workload performance) that I haven't noticed. 

Yeah, very hard, its the tick that starts the balancer, so it would have
to last longer than a tick to be noticed, very unlikely.

We should implement full blown CONFIG_VIRT_CPU_ACCOUNTING,.. except I
bet that once we do that people will want it enabled and I'm pretty sure
people also don't want to pay the price for it... :-)