linux-kernel - Re: [PATCH v2 4/6] KVM-GST: KVM Steal time registration

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Date:	Tue, 01 Feb 2011 15:00:41 -0200
From:	Glauber Costa <glommer@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Avi Kivity <avi@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, aliguori@...ibm.com,
	Rik van Riel <riel@...hat.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	Venkatesh Pallipadi <venki@...gle.com>
Subject: Re: [PATCH v2 4/6] KVM-GST: KVM Steal time registration

> 
> See, that! is the problem, don't round up like that.

Yeah, I was using usecs_to_cputime(), believing this was the standard interface. By the way, one of the things that also led to better results
were just forcing it to 0 every time we had steal == 1 in the end. But
*that* was a real hack =)

> What you can do is: steal_ticks = steal_time_clock() / TICK_NSEC, or
> simply keep a steal time delta and every time it overflows
> cputime_one_jiffy insert a steal-time tick.

What do you think about keeping accounting in msec/usec resolution and
(thus allowing us to compute half a tick to user/system, other half to
steal time) only change it to cputime in the last minute?

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