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Re: [PATCH] Re: [Xen-devel] Time went backwards

To: Rik van Riel <riel@xxxxxxxxxx>
Subject: Re: [PATCH] Re: [Xen-devel] Time went backwards
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Tue, 14 Mar 2006 15:40:08 +0000
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On 14 Mar 2006, at 15:32, Rik van Riel wrote:

Actually, we come into timer_interrupt() sometimes with
blocked + stolen > delta_cpu, so the bugfix is valid.

I just no longer understand how we can get into this
situation...

Could be due to horrendous clock jitter across CPUs. I checked in code yesterday to add a new debug key ('t') to Xen. If you hit that over the serial line, you'll get told the maximum clock difference across CPUs in microseconds. On my system that is usually zero or one microseconds. If it's much much bigger than that on your system then it needs looking into.

 -- Keir


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