linux-kernel - Re: fair group scheduler not so fair?

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Date:	Thu, 29 May 2008 08:20:39 +0530
From:	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
To:	"Chris Friesen" <cfriesen@...tel.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu,
	a.p.zijlstra@...llo.nl, pj@....com,
	Balbir Singh <balbir@...ibm.com>,
	aneesh.kumar@...ux.vnet.ibm.com, dhaval@...ux.vnet.ibm.com
Subject: Re: fair group scheduler not so fair?

On Wed, May 28, 2008 at 12:35:19PM -0600, Chris Friesen wrote:
> Srivatsa Vaddagiri wrote:
>
>> We seem to be skipping the last element in the task list always. In your
>> case, the lone task in Group a/b is always skipped because of this.
>
>> Updated patch (on top of 2.6.26-rc3 +
>> http://programming.kicks-ass.net/kernel-patches/sched-smp-group-fixes/)
>> below.  Pls let me know how it fares!
>
> Looking much better, but still some fairness issues with more complex 
> setups.
>
[snip]

> A 10-sec average was better, but we still see errors of 6%:
> 2478	72.8%
> 2477	64.0%
> 2479	63.2%

Yes I have observed that the delta from ideal fairness is much more than
desirable (although I used to get much better fairness with
2.6.25-rc1. Let me verify and get back).

-- 
Regards,
vatsa
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