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Re: [Xen-devel] A clocksource question

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: Re: [Xen-devel] A clocksource question
From: Joanna Rutkowska <joanna@xxxxxxxxxxxxxxxxxxxxxx>
Date: Sat, 13 Mar 2010 10:58:37 +0100
Cc: Tobias Geiger <tobias.geiger@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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On 03/13/2010 12:48 AM, Jeremy Fitzhardinge wrote:
> 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.
In the meantime found a similar thread on KVM:

and also a patch suggested there:


Don't have time to try the patch right now, but courious to hear your
opinion in the meantime...


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