linux-kernel - Re: 'perf top' broken on intel hybrid systems

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Message-ID: <ZXd64qLLDTEJjSmb@kernel.org>
Date:   Mon, 11 Dec 2023 18:10:58 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     "Liang, Kan" <kan.liang@...ux.intel.com>
Cc:     Ian Rogers <irogers@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        Marc Zyngier <maz@...nel.org>,
        Hector Martin <marcan@...can.st>,
        Namhyung Kim <namhyung@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org
Subject: Re: 'perf top' broken on intel hybrid systems

Em Fri, Dec 08, 2023 at 02:39:37PM -0500, Liang, Kan escreveu:
> On 2023-12-08 1:57 p.m., Arnaldo Carvalho de Melo wrote:
> > 	So I finally got a recent Intel hybrid system:
> > root@...ora:~# grep -m1 "model name" /proc/cpuinfo
> > model name	: Intel(R) Core(TM) i7-14700K
> > root@...ora:~#
> > 	Most things work, but:

> > root@...ora:~# perf top

> > Error:
> > The cycles:P event is not supported.
> > root@...ora:~#
> > 
> > root@...ora:~# perf top -e cycles:p
> > Error:
> > The cycles:p event is not supported.
> > root@...ora:~# perf top -e cycles:pp
> > Error:
> > The cycles:pp event is not supported.
> > ^[[Aroot@...ora:~# perf top -e cycles:ppp
> > Error:
> > The cycles:ppp event is not supported.
> > root@...ora:~#
> > root@...ora:~# perf top -e cycles
> > Error:
> > The cycles event is not supported.
> > root@...ora:~#
 
> The error is because the perf top always tries to open an event on the
> user_requested_cpus, which are all CPUs by default.

But what is wrong with that for the default event, CPU cycles?

It should work for all CPUs, its the most basic event, right?

We should have a rough idea where CPU (no matter which CPUs) cycles are
being used.

- Arnaldo