Re: [tip:perf/core] perf/x86: Use INST_RETIRED.PREC_DIST for cycles: ppp

From: Ingo Molnar
Date: Mon Dec 07 2015 - 01:48:52 EST



* Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> On Sun, Dec 06, 2015 at 02:11:02PM +0100, Ingo Molnar wrote:
>
> > Also, I'm not convinced we need a new 'ppp' qualifier for any of this, why not
> > just replace 'pp' with this event - 'pp' is meant to be our most precise
> > event.
>
> I requested this because the PREC_DIST events can only be scheduled on a single
> counter, whereas the existing :pp events can be had on all 4.
>
> This mean you can have 2 concurrent :pp users (without RR), but not :ppp.

Ok. Will tooling do the right thing? I.e. will the first user of 'perf top' get
:ppp automatically, while the second one falls back to :pp?

Thanks,

Ingo
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