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Date: Mon, 12 Sep 2011 15:47:22 +0530
From: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Turner <pjt@google.com>,
        Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>,
        Vladimir Davydov <vdavydov@parallels.com>,
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        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>
Subject: Re: CFS Bandwidth Control - Test results of cgroups tasks pinned vs
 unpinnede
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* Peter Zijlstra <a.p.zijlstra@chello.nl> [2011-09-09 14:31:02]:

> > Machine : 16-cpus (2 Quad-core w/ HT enabled)
> > Cgroups : 5 in number (C1-C5), each having {2, 2, 4, 8, 16} tasks respectively.
> >           Further, each task is placed in its own (sub-)cgroup with 
> >           a capped usage of 50% CPU.
> 
> So that's loads: {512,512}, {512,512}, {256,256,256,256}, {128,..} and {64,..}

Yes, with the default shares of 1024 for each cgroup.

FWIW we did also try setting shares for each cgroup proportional to number of 
tasks it has. For ex: C1's shares = 1024 * 2 = 2048, C2 = 1024 * 2 = 2048, 
C3 = 4 * 1024 = 4096 etc. while /C1/C1_1, /C1/C1_2, .../C5/C5_16/ shares were 
left at default of 1024 (as those sub-cgroups contain only one task). 
 
That does help reduce idle time by almost 50% (from 15-20% -> 6-9%)

- vatsa