linux-kernel - Re: [PATCH v2 5/6] KVM-GST: adjust scheduler cpu power

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Date:	Tue, 01 Feb 2011 21:04:57 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Glauber Costa <glommer@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	aliguori@...ibm.com, Rik van Riel <riel@...hat.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	Avi Kivity <avi@...hat.com>
Subject: Re: [PATCH v2 5/6] KVM-GST: adjust scheduler cpu power

On Tue, 2011-02-01 at 17:55 -0200, Glauber Costa wrote:
> 
> update_rq_clock_task still have to keep track of what was the last steal
> time value we saw, in the same way it does for irq.

Right, the CONFIG_SCHED_PARAVIRT patch I sent earlier adds a
prev_steal_time member to struct rq for this purpose.

>  One option is to
> call update_rq_clock_task from inside kvm-code, but I don't really like
> it very much.

Why would you need to call anything from the kvm code?

Simply make u64 steal_time_clock(int cpu) a paravirt function with u64
native_steal_time_clock(int cpu) { return 0ULL; }. Possibly avoid the
whole CONFIG_SCHED_PARAVIRT block in update_rq_clock_task() for !
paravirt guests.

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