Subject: Re: [RFC -v2 PATCH 2/3] sched: add yield_to function
From: Mike Galbraith <mgalbraith@suse.de>
To: Avi Kivity <avi@redhat.com>
Cc: Rik van Riel <riel@redhat.com>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Chris Wright <chrisw@sous-sol.org>
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Date: Sat, 18 Dec 2010 20:13:49 +0100
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On Sat, 2010-12-18 at 19:08 +0200, Avi Kivity wrote:
> On 12/17/2010 09:15 AM, Mike Galbraith wrote:
> > BTW, with this vruntime donation thingy, what prevents a task from
> > forking off accomplices who do nothing but wait for a wakeup and
> > yield_to(exploit)?
> >
> 
> What's the difference between that and forking off accomplices who 
> run(exploit) directly?

The clock still advances.  What I described is a clock stopper.

> Many threads dominating the scheduler has been solved by group 
> scheduling.  We need to make sure directed yield doesn't violate that, 
> but I don't see new problems.

Let it become possible to stop clocks, and you surely will :)

	-Mike


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