Re: [PATCH v7 07/12] perf/x86: no counter allocation support

[Wei Wang]

On 07/09/2019 05:43 PM, Peter Zijlstra wrote:
> That's almost a year ago; I really can't remember that and you didn't
> put any of that in your Changelog to help me remember.
>
> (also please use: https://lkml.kernel.org/r/$msgid style links)

OK, I'll put this link in the cover letter or commit log for a reminder.

> > In the previous version, we added a "no_counter" bit to perf_event_attr, and
> > that will be exposed to user ABI, which seems not good.
> > (https://lkml.org/lkml/2019/2/14/791)
> > So we wrap a new kernel API above to support this.
> >
> > Do you have a different suggestion to do this?
> > (exclude host/guest just clears the enable bit when on VM-exit/entry,
> > still consumes the counter)
> Just add an argument to perf_event_create_kernel_counter() ?

Yes. I didn't find a proper place to add this "no_counter" indicator, so 
added a
wrapper to avoid changing existing callers of 
perf_event_create_kernel_counter.

Best,
Wei