linux-kernel - Re: [RFC PATCH 2/3] sched: add yield

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Date:	Fri, 03 Dec 2010 10:35:25 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Mike Galbraith <efault@....de>
CC:	vatsa@...ux.vnet.ibm.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Avi Kiviti <avi@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>,
	Anthony Liguori <aliguori@...ux.vnet.ibm.com>
Subject: Re: [RFC PATCH 2/3] sched: add yield_to function

On 12/03/2010 10:09 AM, Mike Galbraith wrote:
> On Fri, 2010-12-03 at 09:48 -0500, Rik van Riel wrote:
>> On 12/03/2010 09:45 AM, Mike Galbraith wrote:
>>
>>> I'll have to go back and re-read that.  Off the top of my head, I see no
>>> way it could matter which container the numbers live in as long as they
>>> keep advancing, and stay in the same runqueue.  (hm, task weights would
>>> have to be the same too or scaled. dangerous business, tinkering with
>>> vruntimes)
>>
>> They're not necessarily in the same runqueue, the
>> VCPU that is given time might be on another CPU
>> than the one that was spinning on a lock.
>
> I don't think pumping vruntime cross cfs_rq would be safe, for the
> reason noted (et al).  No competition means vruntime is meaningless.
> Donating just advances a clock that nobody's looking at.

Do you have suggestions on what I should do to make
this yield_to functionality work?

I'm willing to implement pretty much anything the
scheduler people will be happy with :)

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