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SubjectRe: [PATCH 2/3] KVM: improve trace events of vmexit/mmio/ioport
On Tue, Jan 17, 2012 at 10:28:11AM +0800, Xiao Guangrong wrote:
> On 01/16/2012 05:38 PM, Avi Kivity wrote:
>
> > On 01/16/2012 11:32 AM, Xiao Guangrong wrote:
> >> - trace vcpu_id for these events
> >
> > We can infer the vcpu id from the kvm_entry tracepoints, no?
> >
>
>
> Thanks for your review, Avi!
>
> Hmm. i think it is hard to do since the vcpu thread can be scheduled
> anytime, one example is as follow:
>
> CPU 0
>
> kvm_entry vcpu 0
> ......
> kvm_entry vcpu 1
> ......
> event1 occurs
> ......
> event2 occurs
>
> It is hard to know the event belong to which kvm_entry?
>
> >> - add kvm_mmio_done to trace the time when mmio/ioport emulation is completed
> >
> > ditto?
> >
>
>
> I think is ok to get the event end time by using kvm_entry.
>
> >
> > Relying on the existing tracepoints will make the tool work on older
> > kernels.
> >
>
>
> We can drop all new events, but unfortunately, the information of the origin
> tracepoints is not enough, at least vcpu_id need be traced in theses events
> to match its events. Yes?

Yes, and if you don't add completed events, you'll have to use kvm_entry
whose collection adds a lot of overhead.



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