linux-kernel - Re: [PATCH v4 1/2] perf: Reveal PMU type in fdinfo

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Message-ID: <CAP-5=fU=5Be2mUL0Ptw1hLG9NuvS9dT1DN83nA2Q9kTskqmh-w@mail.gmail.com>
Date: Mon, 8 Sep 2025 09:42:38 -0700
From: Ian Rogers <irogers@...gle.com>
To: peterz@...radead.org, mingo@...hat.com
Cc: linux-kernel@...r.kernel.org, Chun-Tse Shao <ctshao@...gle.com>, acme@...nel.org, 
	namhyung@...nel.org, mark.rutland@....com, alexander.shishkin@...ux.intel.com, 
	jolsa@...nel.org, adrian.hunter@...el.com, kan.liang@...ux.intel.com, 
	james.clark@...aro.org, howardchu95@...il.com, weilin.wang@...el.com, 
	linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v4 1/2] perf: Reveal PMU type in fdinfo

On Wed, Jul 9, 2025 at 8:25 AM Ian Rogers <irogers@...gle.com> wrote:
>
> On Tue, Jun 24, 2025 at 8:06 PM Ian Rogers <irogers@...gle.com> wrote:
> >
> > On Tue, Jun 3, 2025 at 11:16 AM Chun-Tse Shao <ctshao@...gle.com> wrote:
> > >
> > > It gives useful info on knowing which PMUs are reserved by this process.
> > > Also add config which would be useful.
> > > Testing cycles:
> > >
> > >   $ ./perf stat -e cycles &
> > >   $ cat /proc/`pidof perf`/fdinfo/3
> > >   pos:    0
> > >   flags:  02000002
> > >   mnt_id: 16
> > >   ino:    3081
> > >   perf_event_attr.type:   0
> > >   perf_event_attr.config: 0
> > >
> > > Testing L1-dcache-load-misses:
> > >
> > >   $ ./perf stat -e L1-dcache-load-misses &
> > >   $ cat /proc/`pidof perf`/fdinfo/3
> > >   pos:    0
> > >   flags:  02000002
> > >   mnt_id: 16
> > >   ino:    1072
> > >   perf_event_attr.type:   3
> > >   perf_event_attr.config: 65536
> > >
> > > Reviewed-by: Ian Rogers <irogers@...gle.com>
> > > Signed-off-by: Chun-Tse Shao <ctshao@...gle.com>
> >
> > Ping.
> >
> > Thanks,
> > Ian
>
> Hi Peter and Ingo,
>
> This small kernel change enables being able to better diagnose which
> processes are using perf events for what. In the series it is used in
> perf to blame EBUSY for PMUs like intel-pt on which processes are
> using that PMU.
> Are there issues that need resolving before the patch can be
> considered for inclusion?
>
> The original patch was sent in October 2024:
> https://lore.kernel.org/lkml/20241031223948.4179222-2-ctshao@google.com/

Ping. We're nearly up to a 1 year anniversary on this 10 line change.

Thanks,
Ian