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Re: [Xen-devel] RE: [PATCH] record max stime skew (was RE: [PATCH] stric

To: "dan.magenheimer@xxxxxxxxxx" <dan.magenheimer@xxxxxxxxxx>, "Xen-Devel (E-mail)" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] RE: [PATCH] record max stime skew (was RE: [PATCH] strictly increasing hvm guest time)
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Fri, 04 Jul 2008 20:56:27 +0100
Cc: Dave Winchell <dwinchell@xxxxxxxxxxxxxxx>
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Thread-topic: [Xen-devel] RE: [PATCH] record max stime skew (was RE: [PATCH] strictly increasing hvm guest time)
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On 4/7/08 20:32, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

> Well one suspicion I had was that very long hpet reads were
> getting serialized, but I tried clocksource=acpi and
> clocksource=pit and get similar skew range results.
> In fact pit shows a max of >17000 vs hpet and acpi closer
> to 11000.  (OTOH, I suppose it IS possible that this is
> roughly how long it takes to read each of these platform
> timers.)

That ought to be easy to check. I would expect that the PIT, for example,
could take a couple of microseconds to access.

 -- Keir



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