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Date: Tue, 13 Sep 2011 16:58:52 +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>,
        "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>
Subject: Re: CFS Bandwidth Control - Test results of cgroups tasks pinned vs
 unpinnede
Message-ID: <20110913112852.GE7254@linux.vnet.ibm.com>
Reply-To: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
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* 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?

- vatsa