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