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

[Wangnan (F)]

On 2016/4/15 21:35, Arnaldo Carvalho de Melo wrote:
> 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?

Another question: is it possible to make auxtrace (intel_bts, intel_bt
and coresight) writing to overwritable ring buffer, so we can continuous
trace them and silently drop uninteresting data?

Thank you.

> - 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@xxxxxxxxxx>
> > > > Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> > > > Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> > > > Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> > > > Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> > > > Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> > > > Cc: Zefan Li <lizefan@xxxxxxxxxx>
> > > > Cc: pi3orama@xxxxxxx
> > > > Cc: He Kuang <hekuang@xxxxxxxxxx>
> > > >
> > > > 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