Re: [PATCH RFC 0/2] kvm: Improving directed yield in PLE handler

[Raghavendra K T]

On 07/11/2012 07:29 PM, Raghavendra K T wrote:
> On 07/11/2012 02:30 PM, Avi Kivity wrote:
> > On 07/10/2012 12:47 AM, Andrew Theurer wrote:
> > > For the cpu threads in the host that are actually active (in this case
> > > 1/2 of them), ~50% of their time is in kernel and ~43% in guest. This
> > > is for a no-IO workload, so that's just incredible to see so much cpu
> > > wasted. I feel that 2 important areas to tackle are a more scalable
> > > yield_to() and reducing the number of pause exits itself (hopefully by
> > > just tuning ple_window for the latter).
> >
> > One thing we can do is autotune ple_window. If a ple exit fails to wake
> > anybody (because all vcpus are either running, sleeping, or in ple
> > exits) then we deduce we are not overcommitted and we can increase the
> > ple window. There's the question of how to decrease it again though.
>
> I see some problem here, If I interpret situation correctly. What
> happens if we have two guests with one VM having no over-commit and
> other with high over-commit. (except when we have gang scheduling).
Sorry, I meant less load and high load inside the guest.

> Rather we should have something tied to VM rather than rigid PLE
> window.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/