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

["Wangnan (F)" <wangnan0@huawei.com>]

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@huawei.com>
>>>> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
>>>> Cc: Adrian Hunter <adrian.hunter@intel.com>
>>>> Cc: Jiri Olsa <jolsa@kernel.org>
>>>> Cc: Masami Hiramatsu <mhiramat@kernel.org>
>>>> Cc: Namhyung Kim <namhyung@kernel.org>
>>>> Cc: Zefan Li <lizefan@huawei.com>
>>>> Cc: pi3orama@163.com
>>>> Cc: He Kuang <hekuang@huawei.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