Re: [PATCH v3] perf parse-events: Set exclude_guest=1 for user-space counting

[Jin, Yao]

Hi Arnaldo,

On 8/14/2020 8:47 PM, Arnaldo Carvalho de Melo wrote:
> Em Fri, Aug 14, 2020 at 09:21:20AM +0800, Jin Yao escreveu:
> > Currently if we run 'perf record -e cycles:u', exclude_guest=0.
> >
> > But it doesn't make sense in most cases that we request for
> > user-space counting but we also get the guest report.
> >
> > Of course, we also need to consider perf kvm usage case that
> > authorized perf users on the host may only want to count guest
> > user space events. For example,
> >
> > perf kvm --guest record -e cycles:u
> Ok, probably this works, but what if I want to record guest user samples
> without using 'perf kvm'?
>
> Can we have a 'U' modifier, perhaps, for that?
>
> I.e.
>
> perf record -e cycles:uU would not set exclude_host not exclude_guest,
> cycles:u excludes guest user, cycles:U excludes host user, would that be
> possible?
>
> Anyway, I think that with what we have, your patch makes sense, having a
> way to, without using 'perf kvm' still be able to sample the guest can
> be done on top. of this.
>
> Xu, can we get your Reviewed-by if this addresses your concerns?
>
> - Arnaldo
>   

Do you suggest we will create a new modifier 'U' as a follow-up patch?

cycles:u - Count host user space but it doesn't count the guest user space (exclude_host = 0, 
exclude_guest = 1, exclude_kernel = 1, exclude_user = 0, exclude_hv = 1)

cycles:U - Count the guest user space but it doesn't count the host user space (exclude_host = 1, 
exclude_guest = 0, exclude_kernel = 1, exclude_user = 0, exclude_hv = 1)

Is above understanding correct?

Thanks
Jin Yao