linux-kernel - Re: [RFC -v2 PATCH 2/3] sched: add yield

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Date:	Mon, 20 Dec 2010 11:46:50 +0100
From:	Mike Galbraith <efault@....de>
To:	Avi Kivity <avi@...hat.com>
Cc:	Rik van Riel <riel@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Chris Wright <chrisw@...s-sol.org>
Subject: Re: [RFC -v2 PATCH 2/3] sched: add yield_to function

On Mon, 2010-12-20 at 12:39 +0200, Avi Kivity wrote:
> On 12/20/2010 12:33 PM, Mike Galbraith wrote:
> > >
> > >  Correct.  I don't want the other task to run before me, I just don't
> > >  want to run before it.
> >
> > OK, so what I gather is that if you can preempt another of your own
> > threads to get the target to cpu, that would be a good thing whether
> > he's on the same cpu as yield_to() caller or not.  If the target is
> > sharing a cpu with you, that's even better.  Correct?
> 
> Correct.  I'm not interested in scheduling wrt other tasks, just my tasks.
> 
> However, if I'm all alone on my cpu, and the other task is runnable but 
> not running, behind some unrelated task, then I do need that task to be 
> preempted (or to move tasks around).

So in that case, a pull may be advantageous.

> > Would a kick/hint option be useful?
> 
> Depends on what it does...

Let you decide whether you only want to drop a hint and leave it at
that, or also attempt a preemption.

	-Mike


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