linux-kernel - Re: [PATCH v2 0/6] perf tools: Use SIGUSR2 control data dumpping

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Date:	Fri, 15 Apr 2016 10:35:47 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Adrian Hunter <adrian.hunter@...el.com>
Cc:	Wang Nan <wangnan0@...wei.com>, linux-kernel@...r.kernel.org,
	pi3orama@....com, Arnaldo Carvalho de Melo <acme@...hat.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Zefan Li <lizefan@...wei.com>, He Kuang <hekuang@...wei.com>
Subject: Re: [PATCH v2 0/6] perf tools: Use SIGUSR2 control data dumpping

Em Fri, Apr 15, 2016 at 04:14:26PM +0300, Adrian Hunter escreveu:
> On 15/04/16 03:19, Arnaldo Carvalho de Melo wrote:
> > Em Thu, Apr 14, 2016 at 02:21:59PM +0000, Wang Nan escreveu:
> >> This patch set is based on perf/core.
> >>
> >> v1 -> v2: Fix a bug which triggers output switching without
> >>           '--switch-output' provided.
> >>
> >> Patch 5/10 in v1 has a bug: with following cmdline:
> >>  # perf record -e intel_bts// --per-thread --snapshot -p 13588
> > 
> > Ok, I moved the trigger stuff to a new file, util/trigger.h and added
> > missing man page entries, pushed to acme/perf/core, please take a look
> > if all is well before I push this to Ingo, tomorrow.
> > 
> > Adrian/others, if you can, please take a look.
> 
> Looks OK.  I gave intel_pt a quick test with snapshot mode which didn't seem
> to be broken.
> 
> Using --switch-output with intel_pt gives data that does not decode in the
> 2nd and subsequent files because there is no continuity of switch events.
> Also decoding the last file segfaults because the auxtrace index has not
> been split between the files.

> Probably need to prevent people using --switch-output with intel_pt, but
> I'll look at it more next week.

But the workflow of continuous tracing with regular analysis to go on
dumping uninteresting sections of the trace seems interesting? With the
massive volumes of data with Intel PT continuous tracing is deemded
impossible?

- Arnaldo
 
> > 
> > - Arnaldo
> >  
> >> Sending 'SIGUSR2' to perf triggers output switching, which us
> >> undesirable. The reason is in signal handler perf doesn't consider if
> >> user provided --switch-output explicitly.
> >>
> >> With this patchset applied:
> >>
> >>  # /perf record --switch-output -e intel_bts// --per-thread --snapshot -p 13588 &
> >>  [1] 15116
> >>  # kill -s SIGUSR2 15116
> >>  # [ perf record: dump data: Woken up 5 times ]
> >>  [ perf record: Dump perf.data.2016041506170000 ]
> >>  
> >>  # kill -s SIGUSR2 15116
> >>  # [ perf record: dump data: Woken up 3 times ]
> >>  [ perf record: Dump perf.data.2016041506170447 ]
> >>  
> >>  # fg
> >>  /perf record --switch-output -e intel_bts// --per-thread --snapshot -p 13588
> >>  ^C[ perf record: Woken up 3 times to write data ]
> >>  [ perf record: Dump perf.data.2016041506170785 ]
> >>  [ perf record: Captured and wrote 0.012 MB perf.data.<timestamp> ]
> >>  
> >>  # ls -l ./perf.data*
> >>  -rw------- 1 root root 4212888 Apr 15 06:17 ./perf.data.2016041506170000
> >>  -rw------- 1 root root 4212704 Apr 15 06:17 ./perf.data.2016041506170447
> >>  -rw------- 1 root root   18368 Apr 15 06:17 ./perf.data.2016041506170785
> >>
> >> The first 2 perf.data works fine. The final one has no samples.
> >>
> >> And:
> >>  # rm ./perf.data*
> >>  # /perf record -e intel_bts// --per-thread --snapshot -p 13588 &
> >>  [1] 15396
> >>  # kill -s SIGUSR2 15396
> >>  # kill -s SIGUSR2 15396
> >>  # fg
> >>  /perf record -e intel_bts// --per-thread --snapshot -p 13588
> >>  ^C[ perf record: Woken up 9 times to write data ]
> >>  [ perf record: Captured and wrote 8.012 MB perf.data ]
> >>  
> >>  # ls -l ./perf.data*
> >>  -rw------- 1 root root 8417552 Apr 15 06:20 ./perf.data
> >>
> >> (In v1, the second test trigger output switching incorrectly)
> >>
> >> Patch 1-2/6 in this patchset makes switch output trigger similar to
> >> auxtrace snapshot trigger. Patch 1/6 introduces a 'trigger' class for
> >> them. It would be better to merge patch 1/6 with commit c0bdc1c ("perf
> >> record: Turns auxtrace_snapshot_enable into 3 states"). However, Ingo
> >> has collected that commit, so make it a separated patch.
> >>
> >> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> >> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> >> Cc: Adrian Hunter <adrian.hunter@...el.com>
> >> Cc: Jiri Olsa <jolsa@...nel.org>
> >> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> >> Cc: Namhyung Kim <namhyung@...nel.org>
> >> Cc: Zefan Li <lizefan@...wei.com>
> >> Cc: pi3orama@....com
> >> Cc: He Kuang <hekuang@...wei.com>
> >>
> >> Wang Nan (6):
> >>   perf tools: Extrace trigger class from auxtrace_snapshot
> >>   perf record: Split output into multiple files via '--switch-output'
> >>   perf record: Force enable --timestamp-filename when --switch-output is
> >>     provided
> >>   perf record: Disable buildid cache options by default in switch output
> >>     mode
> >>   perf record: Re-synthesize tracking events after output switching
> >>   perf record: Generate tracking events for process forked by perf
> >>
> >>  tools/perf/builtin-record.c | 147 +++++++++++++++++++++++++++++++-------------
> >>  tools/perf/util/util.h      |  60 ++++++++++++++++++
> >>  2 files changed, 163 insertions(+), 44 deletions(-)
> >>
> >> -- 
> >> 1.8.3.4
> >