RE: [PATCH RFC] KVM: busy-spin detector

Huang, Zhiteng
2010-06-11T15:03:31Z

PLE-like design may be more generic than para-virtish when it comes to Windows guest.

Is this busy-spin actually a Lock Holder Preemption problem?

Regards,

HUANG, Zhiteng

-----Original Message-----
From: kvm-owner@vger.kernel.org [mailto:kvm-owner@vger.kernel.org] On Behalf Of Balbir Singh
Sent: Friday, June 11, 2010 10:07 PM
To: Marcelo Tosatti
Cc: kvm
Subject: Re: [PATCH RFC] KVM: busy-spin detector

* Marcelo Tosatti <mtosatti@redhat.com> [2010-06-10 23:25:51]:

>
> The following patch implements a simple busy-spin detector. It
> considers a vcpu as busy-spinning if there are two consecutive exits
> due to external interrupt on the same RIP, and sleeps for 100us in that case.
>
> It is very likely that if the vcpu is making progress it will either
> exit for other reasons or change RIP.
>
> The percentage numbers below represent improvement in kernel build
> time in comparison with mainline (RHEL 5.4 guest).
>

Interesting approach, is there a reason to tie it in with pause loop exits? Can't we do something more generic or even para-virtish.

--
Three Cheers,
Balbir
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