linux-kernel - Re: [RFC -v5 PATCH 2/4] sched: Add yield

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Date:	Mon, 17 Jan 2011 21:23:16 +0530
From:	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Avi Kiviti <avi@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mike Galbraith <efault@....de>,
	Chris Wright <chrisw@...s-sol.org>, ttracy@...hat.com,
	dshaks@...hat.com
Subject: Re: [RFC -v5 PATCH 2/4] sched: Add yield_to(task, preempt)
 functionality.

On Fri, Jan 14, 2011 at 01:29:52PM -0500, Rik van Riel wrote:
> >I am not sure whether we are meeting that objective via this patch, as
> >lock-spinning vcpu would simply yield after setting next buddy to preferred
> >vcpu on target pcpu, thereby leaking some amount of bandwidth on the pcpu
> >where it is spinning.
> 
> Have you read the patch?

Sorry had mis-read the patch!

On reviewing it further, I am wondering if we can optimize yield_to() further
for case when target and current are on same pcpu, by swapping vruntimes of two
tasks (to let target run in current's place - as we do in task_fork_fair()).

- vatsa
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