linux-kernel - Re: [patch 15/16] sched: return unused runtime on voluntary sleep

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Date:	Tue, 28 Jun 2011 12:01:50 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Paul Turner <pjt@...gle.com>
Cc:	linux-kernel@...r.kernel.org,
	Bharata B Rao <bharata@...ux.vnet.ibm.com>,
	Dhaval Giani <dhaval.giani@...il.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Ingo Molnar <mingo@...e.hu>, Pavel Emelyanov <xemul@...nvz.org>
Subject: Re: [patch 15/16] sched: return unused runtime on voluntary sleep

On Mon, 2011-06-27 at 18:42 -0700, Paul Turner wrote:

> - The aesthetics of releasing rq->lock in the put path.  Quick
> inspection suggests it should actually be safe to do at that point,
> and we do similar for idle_balance().
> 
> Given consideration the above two factors are not requirements, this
> could be moved out of a timer and into the put_path directly (with the
> fact that we drop rq->lock strongly commented).  I have no strong
> preference between either choice.

Argh, ok I see, distribute_cfs_runtime() wants that. Dropping rq->lock
is very fragile esp from the put path, you can only do that _before_ the
put path updates rq->curr etc.. So I'd rather you didn't, just keep the
timer crap and add some comments there.

And we need that distribute_cfs_runtime() muck because that's what
unthrottles rqs when more runtime is available.. bah.


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