RE: [PATCH RFC 00/10] counter read during perf sampling

From	"Liang, Kan" <kan.liang@intel.com>
Newsgroups	linux.kernel
Subject	RE: [PATCH RFC 00/10] counter read during perf sampling
Date	2015-09-28 17:20 +0200
Message-ID	<qdInD-3bi-1@gated-at.bofh.it> (permalink)
References	(1 earlier) <qc9V0-5OU-3@gated-at.bofh.it> <qckGK-4iF-15@gated-at.bofh.it> <qcnbz-7Zv-9@gated-at.bofh.it> <qcCDE-4wT-29@gated-at.bofh.it> <qdqh3-7M-5@gated-at.bofh.it>
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> > >
> > > hum, how the --counter-read-interval data displayed then? it's not
> > > single number right?
> > >
> > No matter which way we choose, I think the output should be similar.
> >
> > As my original design, perf only output every --counter-read-interval
> > data in perf report -D.
> > For tui and stdio, it only output the aggregate number. So, yes, single
> number.
> >
> > I think it should be enough. In tui/stdio, perf gives user a roughly
> > image by the total number during the whole sampling process. If they
> > want details, they can check by report -D.
> > Considering the interval is only 10ms, if perf output everything in
> > tui/stdio, the output is too huge.
> 
> what is the reason to read the counter multiple times

For doing sophisticated memory bandwidth analysis, it requires 10-20ms
interval to read uncore counter.

> if you display only
> single number at the end? overflow issues?
>

Display issue. If we set 10ms interval and do perf record stat for 10s, there
will be 1000 records per cpu. For a system with 64 cpu, there will be 64,000
number. We cannot show all of them in tui/stdio mode.
I think it's better to only show the total number in tui/stdio mode.
If the user want to do sophisticated analysis, they can use -D to dump all
records.

Thanks,
Kan 
 
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[PATCH RFC 00/10] counter read during perf sampling kan.liang@intel.com - 2015-09-22 23:40 +0200
  [PATCH RFC 01/10] perf,tools: Add 'C' event/group modifier kan.liang@intel.com - 2015-09-22 23:40 +0200
  [PATCH RFC 02/10] perf,tools: Enable counter statistic read for perf record kan.liang@intel.com - 2015-09-22 23:40 +0200
  Re: [PATCH RFC 00/10] counter read during perf sampling Jiri Olsa <jolsa@redhat.com> - 2015-09-24 10:20 +0200
    RE: [PATCH RFC 00/10] counter read during perf sampling "Liang, Kan" <kan.liang@intel.com> - 2015-09-24 21:50 +0200
      Re: [PATCH RFC 00/10] counter read during perf sampling Jiri Olsa <jolsa@redhat.com> - 2015-09-25 00:30 +0200
        RE: [PATCH RFC 00/10] counter read during perf sampling "Liang, Kan" <kan.liang@intel.com> - 2015-09-25 17:00 +0200
          Re: [PATCH RFC 00/10] counter read during perf sampling Jiri Olsa <jolsa@redhat.com> - 2015-09-27 22:00 +0200
            RE: [PATCH RFC 00/10] counter read during perf sampling "Liang, Kan" <kan.liang@intel.com> - 2015-09-28 17:20 +0200

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