linux-kernel - Re: CFS Bandwidth Control - Test results of cgroups tasks pinned vs unpinnede

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Message-ID: <20110913112852.GE7254@linux.vnet.ibm.com>
Date:	Tue, 13 Sep 2011 16:58:52 +0530
From:	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Paul Turner <pjt@...gle.com>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	Vladimir Davydov <vdavydov@...allels.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Bharata B Rao <bharata@...ux.vnet.ibm.com>,
	Dhaval Giani <dhaval.giani@...il.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Pavel Emelianov <xemul@...allels.com>
Subject: Re: CFS Bandwidth Control - Test results of cgroups tasks pinned vs
 unpinnede

* Peter Zijlstra <a.p.zijlstra@...llo.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
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