linux-kernel - Re: [PATCH v2 2/2] perf stat: Support regex pattern in --for-each-cgroup

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Date:   Mon, 26 Oct 2020 14:53:49 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Jiri Olsa <jolsa@...hat.com>, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Ian Rogers <irogers@...gle.com>
Subject: Re: [PATCH v2 2/2] perf stat: Support regex pattern in
 --for-each-cgroup

Em Mon, Oct 26, 2020 at 09:32:34PM +0900, Namhyung Kim escreveu:
> Hi Jiri,
> 
> On Mon, Oct 26, 2020 at 8:40 PM Jiri Olsa <jolsa@...hat.com> wrote:
> >
> > On Sat, Oct 24, 2020 at 11:59:18AM +0900, Namhyung Kim wrote:
> > > To make the command line even more compact with cgroups, support regex
> > > pattern matching in cgroup names.
> > >
> > >   $ perf stat -a -e cpu-clock,cycles --for-each-cgroup ^foo sleep 1
> > >
> > >           3,000.73 msec cpu-clock                 foo #    2.998 CPUs utilized
> > >     12,530,992,699      cycles                    foo #    7.517 GHz                      (100.00%)
> > >           1,000.61 msec cpu-clock                 foo/bar #    1.000 CPUs utilized
> > >      4,178,529,579      cycles                    foo/bar #    2.506 GHz                      (100.00%)
> > >           1,000.03 msec cpu-clock                 foo/baz #    0.999 CPUs utilized
> > >      4,176,104,315      cycles                    foo/baz #    2.505 GHz                      (100.00%)
> >
> > just curious.. there was another foo/XXX group using the
> > rest of the cycles, right?
> 
> No, if so it should be displayed too.  But actually there was a process
> in the foo cgroup itself.
> 
> >
> > also perhaps we want to warn if there's no match found:
> >
> >         $ sudo ./perf stat -a -e cpu-clock,cycles --for-each-cgroup ^foo sleep 1
> >
> >          Performance counter stats for 'system wide':
> >
> >
> >                1.002375575 seconds time elapsed
> >
> 
> Right, will check this case.

Hum, I thought that could be done on top of this one, but then, the
ambiguity of:

1. No samples for a cgroups matching that expression

2. No cgroups match that expression

Is real and warrants a warning for the 'no cgroups match the
--for-each-group regexp' case.

So I'll wait for v3 with that warning,

Thanks,

- Arnaldo