linux-kernel - Re: [PATCH] perf stat: Ensure group is defined on top of the same cpu mask

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Date:   Mon, 1 Jun 2020 09:40:16 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jin Yao <yao.jin@...ux.intel.com>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Michael Petlan <mpetlan@...hat.com>,
        Stephane Eranian <eranian@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH] perf stat: Ensure group is defined on top of the same
 cpu mask

On Sun, May 31, 2020 at 05:04:47PM -0700, Ian Rogers wrote:
> On Sun, May 31, 2020 at 9:22 AM Jiri Olsa <jolsa@...nel.org> wrote:
> >
> > Jin Yao reported the issue (and posted first versions of this change)
> > with groups being defined over events with different cpu mask.
> >
> > This causes assert aborts in get_group_fd, like:
> >
> >   # perf stat -M "C2_Pkg_Residency" -a -- sleep 1
> >   perf: util/evsel.c:1464: get_group_fd: Assertion `!(fd == -1)' failed.
> >   Aborted
> >
> > All the events in the group have to be defined over the same
> > cpus so the group_fd can be found for every leader/member pair.
> >
> > Adding check to ensure this condition is met and removing the
> > group (with warning) if we detect mixed cpus, like:
> >
> >   $ sudo perf stat -e '{power/energy-cores/,cycles},{instructions,power/energy-cores/}'
> >   WARNING: event cpu maps do not match, disabling group:
> >     anon group { power/energy-cores/, cycles }
> >     anon group { instructions, power/energy-cores/ }
> 
> This is really cool! I wonder if there is a better wording for 'event
> cpu maps' ? It may be useful to list what the cpu maps are for the
> events as a diagnostic aid.

right, we could display that for -v option

jirka