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Re: [Xen-devel] pv_ops (2.6.31) and CONFIG_NO_HZ

To: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, "Xen-Devel (E-mail)" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] pv_ops (2.6.31) and CONFIG_NO_HZ
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Tue, 03 Nov 2009 07:41:07 +0000
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
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On 02/11/2009 22:29, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

> But as long as we are on the PV topic: Does this mean that
> a PV guest that is idle will never get scheduled due to
> needing to process a tick?  I do see that an idle
> PV domain is doing about 250 kernel rdtsc/second, so
> is this just because the Xen scheduler has nothing
> better to do with a pcpu so it schedules an "idle"
> vcpu on it?

A PV guest is supposed to set a one-shot timer on the next event in its
timer queues. So it depends what sorts of events get put on its timer queues
-- if there are periodic events, it will still request seemingly periodic
one-shot wakeups.

 -- Keir

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