linux-kernel - Re: [RFC PATCH v1 0/4] CFS Bandwidth Control

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Date:	Tue, 16 Feb 2010 11:48:18 +0530
From:	Bharata B Rao <bharata@...ux.vnet.ibm.com>
To:	Paul Turner <pjt@...gle.com>
Cc:	linux-kernel@...r.kernel.org, Paul Menage <menage@...gle.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Gautham R Shenoy <ego@...ibm.com>,
	Dhaval Giani <dhaval.giani@...il.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Herbert Poetzl <herbert@...hfloor.at>,
	Chris Friesen <cfriesen@...tel.com>,
	Avi Kivity <avi@...hat.com>, Nikhil Rao <ncrao@...gle.com>,
	Ingo Molnar <mingo@...e.hu>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	Mike Waychison <mikew@...gle.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Pavel Emelyanov <xemul@...nvz.org>
Subject: Re: [RFC PATCH v1 0/4] CFS Bandwidth Control

On Fri, Feb 12, 2010 at 06:54:52PM -0800, Paul Turner wrote:
> Todo:
> -----
> - hierarchal nr_tasks_running accounting:
>   This is a deficiency currently shared with SCHED_RT rate limiting.  When
>   entities is throttled the running tasks it owns are not subtracted from 
>   rq->nr_running.  This then results in us missing idle_balance() due to
>   phantom tasks and load balancer weight per task calculations being
>   incorrect.
> 
>   This code adds complexity which was both increasing the complexity of the
>   initial review for this patchset and truly probably best reviewed
>   independently of this feature's scope.  To that end we'll post a separate
>   patch for this issue against the current RT rate-limiting code and merge any 
>   converged on approach here as appropriate.

I had tried updating rq->nr_running in my v2 patchset
(http://lkml.org/lkml/2009/9/30/117, http://lkml.org/lkml/2009/9/30/119)
But since I felt that it added a lot of complexity, I removed it
subsequently in v3 (http://lkml.org/lkml/2009/11/9/65) and kept it similar
to RT.

> 
> - throttle statistics:
>   Some statistics regarding the frequency and duration of throttling
>   definitely in order.

Please take a look at some of the throttling related stats I am collecting
in my patchset.

Regards,
Bharata.

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