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Re: [Xen-devel] [PATCH] LAPIC timer accounting fix

To: Ben Guthro <bguthro@xxxxxxxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Gary Grebus <ggrebus@xxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] LAPIC timer accounting fix
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Thu, 25 Oct 2007 15:16:26 +0100
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On 24/10/07 22:12, "Ben Guthro" <bguthro@xxxxxxxxxxxxxxx> wrote:

> Offset emulated local APIC timer so it doesn't tick during guest's
> timer related processing. Otherwise, guests using the local APIC for
> process accounting can see long sequences of process ticks incorrectly
> charged to interrupt processing.

Do they really get in sync like that? Seems a bit odd. Couldn't the same
happen on real hardware? I wonder why it would be more likely in the
virtualised case...

Perhaps just offsetting all periodic timers by some random fraction of the
period would be a simpler patch?

 -- Keir



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