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Re: [Xen-devel] A clocksource question

To: Joanna Rutkowska <joanna@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] A clocksource question
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Fri, 12 Mar 2010 15:48:45 -0800
Cc: Tobias Geiger <tobias.geiger@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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On 03/12/2010 01:13 PM, Joanna Rutkowska wrote:

The "clocksource tsc unstable" messages trouble me too BTW. They seem to
appear before the hrtimer "interrupt too slow" messages.

But this "tsc unstable" message does not seem to be so critical,

They're nothing to worry about.

  e.g. I
just started my system (xen clocksource) and started a VM, and got the
usual hrtimer "slow interrupt" warning, and then all the symptoms
started, but there no "tsc unstables" warning in dmesg.

However, I previously missed another message, that seem to occur at the
very beginning of the system life (before I started any other VMs):

Marking TSC unstable due to TSC halts in idle

That doesn't matter because it doesn't use the tsc clocksource. The Xen clocksource uses the tsc hardware register, but it isn't subject to the same constraints that the tsc clocksource is. The tsc clocksource calibration is probably getting confused by being on a vcpu.


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