linux-kernel - Re: [PATCHSET v3 0/3] perf tools: Minor improvements in event synthesis

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Date:   Wed, 3 Feb 2021 10:09:53 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Namhyung Kim <namhyung@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        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: [PATCHSET v3 0/3] perf tools: Minor improvements in event
 synthesis

Em Tue, Feb 02, 2021 at 01:40:07PM +0100, Jiri Olsa escreveu:
> On Tue, Feb 02, 2021 at 06:01:15PM +0900, Namhyung Kim wrote:
> > Hello,
> > 
> > This is to optimize the event synthesis during perf record.
> > 
> > Changes in v3:
> >  * remove unnecessary pid check
> >  * update change log in patch #2
> 
> Acked-by: Jiri Olsa <jolsa@...hat.com>

Thanks, applied.

- Arnaldo

 
> thanks,
> jirka
> 
> > 
> > The first patch is to reduce memory usage when many threads are used.
> > The second is to avoid unncessary syscalls for kernel threads.  And
> > the last one is to reduce the number of threads to iterate when new
> > threads are being created at the same time.
> > 
> > Unfortunately there's no dramatic improvement here but I can see ~5%
> > gain in the 'perf bench internals synthesize' on a big machine.
> > (The numbers are not stable though)
> > 
> > 
> > Before:
> >   # perf bench internals synthesize --mt -M1 -I 100
> >   # Running 'internals/synthesize' benchmark:
> >   Computing performance of multi threaded perf event synthesis by
> >   synthesizing events on CPU 0:
> >     Number of synthesis threads: 1
> >       Average synthesis took: 68831.480 usec (+- 101.450 usec)
> >       Average num. events: 9982.000 (+- 0.000)
> >       Average time per event 6.896 usec
> > 
> > 
> > After:
> >   # perf bench internals synthesize --mt -M1 -I 100
> >   # Running 'internals/synthesize' benchmark:
> >   Computing performance of multi threaded perf event synthesis by
> >   synthesizing events on CPU 0:
> >     Number of synthesis threads: 1
> >       Average synthesis took: 65036.370 usec (+- 158.121 usec)
> >       Average num. events: 9982.000 (+- 0.000)
> >       Average time per event 6.515 usec
> > 
> > 
> > Thanks,
> > Namhyung
> > 
> > 
> > Namhyung Kim (3):
> >   perf tools: Use /proc/<PID>/task/<TID>/status for synthesis
> >   perf tools: Skip MMAP record synthesis for kernel threads
> >   perf tools: Use scandir() to iterate threads
> > 
> >  tools/perf/util/synthetic-events.c | 83 +++++++++++++++++++-----------
> >  1 file changed, 53 insertions(+), 30 deletions(-)
> > 
> > -- 
> > 2.30.0.365.g02bc693789-goog
> > 
> 

-- 

- Arnaldo