Re: [Xen-devel] A clocksource question

[Joanna Rutkowska <joanna@xxxxxxxxxxxxxxxxxxxxxx>]

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:
http://www.mail-archive.com/kvm@xxxxxxxxxxxxxxx/msg22925.html

and also a patch suggested there:

http://www.mail-archive.com/kvm@xxxxxxxxxxxxxxx/msg23491.html

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

Thanks,
joanna.

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