Re: [PATCH v4 0/8] KVM paravirt remote flush tlb

Nikunj A Dadhania
2012-09-04T01:31:18Z

On Mon, 03 Sep 2012 17:33:46 +0300, Avi Kivity <avi@redhat.com> wrote:
> On 08/21/2012 02:25 PM, Nikunj A. Dadhania wrote:
> >
> > kernbench(lower is better)
> > ==========================
> > base pvflushv4 %improvement
> > 1VM 48.5800 46.8513 3.55846
> > 2VM 108.1823 104.6410 3.27346
> > 3VM 183.2733 163.3547 10.86825
> >
> > ebizzy(higher is better)
> > ========================
> > base pvflushv4 %improvement
> > 1VM 2414.5000 2089.8750 -13.44481
> > 2VM 2167.6250 2371.7500 9.41699
> > 3VM 1600.1111 2102.5556 31.40060
> >
>
> The regression is worrying. We're improving the contended case at the
> cost of the non-contended case, this is usually the wrong thing to do.
> Do we have any clear idea of the cause of the regression?
>
Previous perf numbers suggest that in 1VM scenario flush_tlb_others_ipi
is around 2%, while for contented case its around 10%. That is what is
helping contended case.

Regards,
Nikunj