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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>
Date: Tue, 13 Sep 2011 16:07:28 +0200
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On Tue, 2011-09-13 at 16:58 +0530, Srivatsa Vaddagiri wrote:
> * Peter Zijlstra <a.p.zijlstra@chello.nl> [2011-09-13 11:39:48]:
> 
> > On Tue, 2011-09-13 at 10:33 +0530, Srivatsa Vaddagiri wrote:
> > > 
> > > This is perhaps not optimal (as it may lead to more lock contentions), but 
> > > something to note for those who care for both capping and utilization in
> > > equal measure!
> > 
> > You meant lock inversion, which leads to more idle time :-)
> 
> I think 'cfs_b->lock' contention would go up significantly when reducing
> sysctl_sched_cfs_bandwidth_slice, while for something like 'balancing' lock 
> (taken with SD_SERIALIZE set and more frequently when tuning down
> max_interval?), yes it may increase idle time! Did you have any other
> lock in mind when speaking of inversion?

I can't read it seems.. I thought you were talking about increasing the
period, which increases the time you force a task to sleep that's
holding locks etc..