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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

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.

There is no easy solution to this problem.

~Andrew

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