Re: [Xen-devel] PV performance degraded after live migration

[Juergen Gross <jgross@xxxxxxxx>]

On 15/03/17 16:26, Andrew Cooper wrote:
> On 15/03/17 15:23, Olaf Hering wrote:
>> On Wed, Mar 15, Olaf Hering wrote:
>>
>>> On Wed, Mar 15, Andrew Cooper wrote:
>>>> As a crazy idea, doest this help?
>>>> tsc->incarnation = 0
>> This does indeed help. One system shows now the results below, which
>> means the performance goes down during migration (to localhost) and goes
>> back to normal after migration.
>>
>> What impact has such change to ->incarnation?
> 
> So what this means is that, after migrate, Xen sees that the advertised
> TSC value doesn't match the current hardwares TSC, so enables rdtsc
> interception so the values reported back can be emulated at the old
> frequency.

Why does Xen detect a different frequency after a localhost migration?


Juergen

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