linux-kernel - Re: [PATCH v4 8/9] KVM-GST: adjust scheduler cpu power

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Message-ID: <1309602682.10073.25.camel@twins>
Date:	Sat, 02 Jul 2011 12:31:22 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Glauber Costa <glommer@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Rik van Riel <riel@...hat.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	Avi Kivity <avi@...hat.com>,
	Anthony Liguori <aliguori@...ibm.com>,
	Eric B Munson <emunson@...bm.net>
Subject: Re: [PATCH v4 8/9] KVM-GST: adjust scheduler cpu power

On Fri, 2011-07-01 at 17:22 -0400, Glauber Costa wrote:
> This patch makes update_rq_clock() aware of steal time.
> The mechanism of operation is not different from irq_time,
> and follows the same principles. This lives in a CONFIG
> option itself, and can be compiled out independently of
> the rest of steal time reporting. The effect of disabling it
> is that the scheduler will still report steal time (that cannot be
> disabled), but won't use this information for cpu power adjustments.
> 
> Everytime update_rq_clock_task() is invoked, we query information
> about how much time was stolen since last call, and feed it into
> sched_rt_avg_update().
> 
> Although steal time reporting in account_process_tick() keeps
> track of the last time we read the steal clock, in prev_steal_time,
> this patch do it independently using another field,
> prev_steal_time_rq. This is because otherwise, information about time
> accounted in update_process_tick() would never reach us in update_rq_clock().
> 
> Signed-off-by: Glauber Costa <glommer@...hat.com>
> CC: Rik van Riel <riel@...hat.com>
> CC: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
> CC: Peter Zijlstra <peterz@...radead.org>
> CC: Avi Kivity <avi@...hat.com>
> CC: Anthony Liguori <aliguori@...ibm.com>
> CC: Eric B Munson <emunson@...bm.net>

Acked-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>

Cleaning up that CPP mess when the GCC people come back saying their
compiler will properly do that optimization can always be done in a
follow up patch.

Thanks!
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