linux-kernel - Re: [PATCHv2] perf stat: Ensure group is defined on top of the same cpu mask

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Date:   Tue, 2 Jun 2020 10:25:35 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Jin Yao <yao.jin@...ux.intel.com>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...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: [PATCHv2] perf stat: Ensure group is defined on top of the same
 cpu mask

Em Tue, Jun 02, 2020 at 02:10:17PM +0200, Jiri Olsa escreveu:
> On Tue, Jun 02, 2020 at 08:50:17PM +0900, Namhyung Kim wrote:
> > Hi Jiri,
> > 
> > On Tue, Jun 2, 2020 at 5:16 PM Jiri Olsa <jolsa@...hat.com> wrote:
> > >
> > > On Tue, Jun 02, 2020 at 11:47:19AM +0900, Namhyung Kim wrote:
> > > > On Tue, Jun 2, 2020 at 1:21 AM Ian Rogers <irogers@...gle.com> wrote:
> > > > >
> > > > > On Mon, Jun 1, 2020 at 1:20 AM Jiri Olsa <jolsa@...hat.com> 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/ }
> > > > > >
> > > > > > Ian asked also for cpu maps details, it's displayed in verbose mode:
> > > > > >
> > > > > >   $ sudo perf stat -e '{cycles,power/energy-cores/}' -v
> > > > > >   WARNING: group events cpu maps do not match, disabling group:
> > > > > >     anon group { power/energy-cores/, cycles }
> > > > > >        power/energy-cores/: 0
> > > > > >        cycles: 0-7
> > > > > >     anon group { instructions, power/energy-cores/ }
> > > > > >        instructions: 0-7
> > > > > >        power/energy-cores/: 0
> > > > >
> > > > > This is great! A nit, would 'grouped events cpus do not match' read
> > > > > better? I think the cpu map is more of an internal naming convention.
> > > > Allowed cpus?
> > >
> > > hum, what you mean?
> > 
> > I mean that we can use 'allowed cpus' rather then 'cpu map' in the message.
> > Something like this?
> > 
> >   allowed cpus for events in a group do not match, disabling group:
> 
> hm, I like more the one Ian suggested.. anyway, leaving this to Arnaldo,
> he can change that before committing ;-)

I think its ok as-is, Ian, can I have your acked-by?

- Arnaldo