linux-kernel - Re: perf-stat per thread results

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Date:	Sat, 14 May 2011 11:48:24 -0600
From:	David Ahern <dsahern@...il.com>
To:	Wim Heirman <wim@...rman.net>
CC:	Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Brice Goglin <Brice.Goglin@...ia.fr>
Subject: Re: perf-stat per thread results

On 05/14/11 06:49, Wim Heirman wrote:
>> Hmm.... my mileage varies using latest kernel
>> (446cc6345d3de6571bdd0840f48aca441488a28d)
>>
>> $ /tmp/build-perf/perf record --stat -fo /tmp/perf.data -p $(pidof rsyslogd)
>> ^C[ perf record: Woken up 1 times to write data ]
>> [ perf record: Captured and wrote 0.007 MB /tmp/perf.data (~308 samples) ]
>>
>> $ /tmp/build-perf/perf report -T -i /tmp/perf.data
>> # Events: 6  cycles
>> #
>> # Overhead   Command      Shared Object                      Symbol
>> # ........  ........  .................  ..........................
>> #
>>    97.61%  rsyslogd  libc-2.13.so       [.] __libc_disable_asynccancel
>>     2.39%  rsyslogd  [kernel.kallsyms]  [k] native_write_msr_safe
>>
>>
>> #
>> # (For a higher level overview, try: perf report --sort comm,dso)
>> #
>> # PID  TID
>>
>>
>> ie., I do not get the counter values. Specifying the counter with -e
>> (e.g., -e branch-misses) does not help -- still no counter output.
> 
> Is rsyslogd multithreaded? (Or at least, do the non-main threads
> execute any work during your perf-record measurement) If not, then
> what you see is consistent with what I'm getting, i.e. everything but
> the main thread is reported.

It is multithreaded, but my point is that I do not get counter output at
the end -- the PID/TID table is empty. I do not get counters for single
threaded processes nor for commands run by perf record -- e.g.,
/tmp/build-perf/perf record --stat -e instructions -fo /tmp/perf.data --
sleep 1

David


> 
> Regards,
> Wim
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