linux-kernel - Re: [PATCH v5 13/13] perf record: introduce --ctl-fd[-ack] options

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Message-ID: <0a2695a1-06e4-678f-736c-1560222826de@linux.intel.com>
Date:   Mon, 8 Jun 2020 11:04:36 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 13/13] perf record: introduce --ctl-fd[-ack] options


On 05.06.2020 18:23, Alexey Budankov wrote:
> 
> On 05.06.2020 17:47, Alexey Budankov wrote:
>>
>> On 05.06.2020 16:57, Jiri Olsa wrote:
>>> On Fri, Jun 05, 2020 at 04:15:52PM +0300, Alexey Budankov wrote:
>>>>
>>>> On 05.06.2020 13:51, Jiri Olsa wrote:
>>>>> On Tue, Jun 02, 2020 at 04:43:58PM +0300, Adrian Hunter wrote:
>>>>>> On 2/06/20 12:12 pm, Alexey Budankov wrote:
>>>>>>>
>>>>>>> On 02.06.2020 11:32, Alexey Budankov wrote:
>>>>>>>>
>>>>>>>> On 02.06.2020 2:37, Andi Kleen wrote:
>>>>>>>>>>> or a pathname, or including also the event default of "disabled".
>>>>>>>>>>
>>>>>>>>>> For my cases conversion of pathnames into open fds belongs to external
>>>>>>>>>> controlling process e.g. like in the examples provided in the patch set.
>>>>>>>>>> Not sure about "event default of 'disabled'"
>>>>>>>>>
>>>>>>>>> It would be nicer for manual use cases if perf supported the path names
>>>>>>>>> directly like in Adrian's example, not needing a complex wrapper script.
>>>>>>>>
>>>>>>>> fds interface is required for VTune integration since VTune wants control
>>>>>>>> over files creation aside of Perf tool process. The script demonstrates
>>>>>>>> just one possible use case.
>>>>>>>>
>>>>>>>> Control files could easily be implemented on top of fds making open operations
>>>>>>>> for paths and then initializing fds. Interface below is vague and with explicit
>>>>>>>> options like below it could be more explicit:
>>>>>>>> --ctl-file /tmp/my-perf.fifo --ctl-file-ack /tmp/my-perf-ack.fifo
>>>>>>>
>>>>>>> Or even clearer:
>>>>>>>
>>>>>>> --ctl-fifo /tmp/my-perf --ctl-fifo-ack /tmp/my-perf-ack
>>>>>>
>>>>>> If people are OK with having so many options, then that is fine by me.
>>>>>
>>>>> the single option Adrian suggested seems better to me:
>>>>>
>>>>>  --control
>>>>>  --control 11
>>>>>  --control 11,15
>>>>
>>>> What if a user specifies fifos named like this above, not fds?
>>>>
>>>>>  --control 11,15,disabled
>>>>>  --control 11,,disabled
>>>>>  --control /tmp/my-perf.fifo
>>>>>  --control /tmp/my-perf.fifo,/tmp/my-perf-ack.fifo
>>>>
>>>> What if a user wants not fifos but other type of comm channels?
>>>>
>>>>>  --control /tmp/my-perf.fifo,/tmp/my-perf-ack.fifo,disabled
>>>>>  --control /tmp/my-perf.fifo,,disabled
>>>>>
>>>>> we already support this kind of options arguments, like for --call-graph
>>>>>
>>>>> jirka
>>>>>
>>>>
>>>> IMHO,
>>>> this interface, of course, looks more compact (in amount of options) however
>>>> the other side it is less user friendly. One simple option for one simple
>>>> purpose is more convenient as for users as for developers. Also complex
>>>> option syntax tends to have limitations and there are probably more
>>>> non-obvious ones.
>>>>
>>>> Please speak up. I might have missed something meaningful.
>>>
>>> how about specify the type like:
>>>
>>> --control fd:1,2,...
>>
>> What do these ... mean?
> 
> After all,
> if you want it this way and it now also fits my needs I could convert
> --ctl-fd[-ack] to --control fd:<ctl-fd>,<ack-fd> with use cases like
> --control fd:<ctl-fd> and --control fd:<ctl-fd>,<ack-fd>. Accepted?

So, do we implement fds options like this?

~Alexey