RE: [PATCH v1] KVM/x86/vPMU: Guest PMI Optimization

[Wang, Wei W]

On Saturday, October 13, 2018 12:31 AM, Andi Kleen wrote:
> > 4. Results
> >     - Without this optimization, the guest pmi handling time is
> >       ~4500000 ns, and the max sampling rate is reduced to 250.
> >     - With this optimization, the guest pmi handling time is ~9000 ns
> >       (i.e. 1 / 500 of the non-optimization case), and the max sampling
> >       rate remains at the original 100000.
> 
> Impressive performance improvement!
> 
> It's not clear to me why you're special casing PMIs here. The optimization
> should work generically, right?


Yes, seems doable. I plan to try some lazy approach for the perf event allocation. 

> Is that guaranteed to be always called on the right CPU that will run the vcpu?
> 
> AFAIK there's an ioctl to set MSRs in the guest from qemu, I'm pretty sure it
> won't handle that.
 

Thanks, will consider that case.

Best,
Wei