linux-kernel - Re: [PATCH v4 1/6] perf tools: Derive trigger class from auxtrace

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Date:	Mon, 18 Apr 2016 22:37:04 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	Jiri Olsa <jolsa@...hat.com>
CC:	<acme@...nel.org>, <linux-kernel@...r.kernel.org>,
	<pi3orama@....com>, Adrian Hunter <adrian.hunter@...el.com>,
	He Kuang <hekuang@...wei.com>, Jiri Olsa <jolsa@...nel.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Zefan Li <lizefan@...wei.com>
Subject: Re: [PATCH v4 1/6] perf tools: Derive trigger class from
 auxtrace_snapshot



On 2016/4/18 22:29, Jiri Olsa wrote:
> On Mon, Apr 18, 2016 at 10:20:23PM +0800, Wangnan (F) wrote:
>>
>> On 2016/4/18 21:45, Jiri Olsa wrote:
>>> On Mon, Apr 18, 2016 at 06:32:08AM +0000, Wang Nan wrote:
>>>> Use 'trigger' to model operations which need to be executed when
>>>> an event (a signal, for example) is observed.
>>>>
>>>> States and transits:
>>>>
>>>>   OFF--(on)--> READY --(toggle)--> TOGGLED --(process)--> PROCESSING
>>>>                  ^                    |                      |
>>>>                  |                    |                      |
>>>>                  |                 (ready)                (ready)
>>>>                  |                    |                      |
>>>>                   \__________________/______________________/
>>>>
>>>> is_toggled and is_ready are two key functions to query the state of
>>>> a trigger. is_toggled means the event already happen; is_ready means the
>>>> trigger is waiting for the event.
>>>>
>>>> 'PROCESSING' represents a state the event happens and be observed, and
>>>> the processing is on the way so can't accept a new event immediately.
>>> hum, I must be missing something.. but I dont see how you're
>>> using this state except for smal window within:
>>>
>>>                  if (auxtrace_snapshot_is_toggled()) {
>>>   ->                     auxtrace_snapshot_process();
>>>                          if (!auxtrace_snapshot_is_error())
>>>   ->                              record__read_auxtrace_snapshot(rec);
>>>
>>> but no other place queries or depends on this state
>> Right.
>>
>> Since we are creating a new class, I think we can make code simpler by
>> merging
>> all state variables into trigger.
>>
>> Without this state we must keep 'auxtrace_record__snapshot_started'.
> do we? we dont need this for switch_output code apparently

I think it is a good chance to clean existing code.

However, number of lines introduced to .h in patch 1/6 is more than
lines removed from .c. So I think removing the 'PROCESSING' is okay.
If in future we find switch_output also need this state we can add it
back at that time.

Please wait for v5.

Thank you.

> jirka
>
>> I think merging it into trigger class makes the whole program a little
>> bit simpler. Or do you think keeping trigger class simpler whould be better?
>>
>> Thank you.
>>
>>