linux-kernel - Re: Invalid event (cycles:pp) in per-thread mode, enable system wide with '-a'.

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Message-ID: <CAM9d7chvZjZ4YVc6j3w7OkdHteyJ0GUZboieu9G7jAWBevoZqA@mail.gmail.com>
Date:   Thu, 29 Sep 2022 21:26:31 -0700
From:   Namhyung Kim <namhyung@...il.com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Slade Watkins <srw@...dewatkins.net>,
        Ravi Bangoria <ravi.bangoria@....com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: Invalid event (cycles:pp) in per-thread mode, enable system wide
 with '-a'.

Hello,

On Thu, Sep 29, 2022 at 8:49 PM Ian Rogers <irogers@...gle.com> wrote:
>
> On Thu, Sep 29, 2022 at 3:10 PM Slade Watkins <srw@...dewatkins.net> wrote:
> >
> > Hey Nick,
> >
> > > On Sep 29, 2022, at 5:54 PM, Nick Desaulniers <ndesaulniers@...gle.com> wrote:
> > >
> > > I remember hearing rumblings about issues with zen 2, LBR, vs zen 3.
> > > Is this a known issue, or am I holding it wrong?
> >
> > Hm… I also remember this. I have a Zen 2 based system that I can do testing on, so I will do so when I’m able.
> >
> > If I discover something of note, I’ll get back to you.
> >
> > Cheers,
> > -srw
> >
>
> LBR isn't yet supported for Zen but is coming:
> https://lore.kernel.org/lkml/166155216401.401.5809694678609694438.tip-bot2@tip-bot2/
> I'd recommend frame-pointers.
>
> +Ravi who may be able to say if there are any issues with the precise
> sampling on AMD.

Afaik cvcles:pp will use IBS but it doesn't support per-task profiling
since it has no task context.  Ravi is working on it..

Thanks,
Namhyung