Subject: Re: [RFC PATCH 2/3] sched: add yield_to function
From: Mike Galbraith <efault@gmx.de>
To: Rik van Riel <riel@redhat.com>
Cc: vatsa@linux.vnet.ibm.com, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, Avi Kiviti <avi@redhat.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>, Ingo Molnar <mingo@elte.hu>,
        Anthony Liguori <aliguori@linux.vnet.ibm.com>
In-Reply-To: <4CF90341.4020101@redhat.com>
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	 <1291355656.7633.124.camel@marge.simson.net>
	 <20101203134618.GG27994@linux.vnet.ibm.com>
	 <1291387511.7992.15.camel@marge.simson.net>  <4CF90341.4020101@redhat.com>
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Date: Fri, 03 Dec 2010 16:09:47 +0100
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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.

	-Mike

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