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

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Date:	Thu, 23 Jun 2011 17:26:18 +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 Tue, 2011-06-21 at 00:17 -0700, Paul Turner wrote:
> plain text document attachment (sched-bwc-simple_return_quota.patch)
> When a local cfs_rq blocks we return the majority of its remaining quota to the
> global bandwidth pool for use by other runqueues.

OK, I saw return_cfs_rq_runtime() do that.

> We do this only when the quota is current and there is more than 
> min_cfs_rq_quota [1ms by default] of runtime remaining on the rq.

sure..

> In the case where there are throttled runqueues and we have sufficient
> bandwidth to meter out a slice, a second timer is kicked off to handle this
> delivery, unthrottling where appropriate.

I'm having trouble there, what's the purpose of the timer, you could
redistribute immediately. None of this is well explained.
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