linux-kernel - Re: Re: [PATCH v3 5/5] perf/sdt: Add support to perf record to trace SDT events

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Date:	Thu, 23 Oct 2014 17:57:34 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Hemant Kumar <hemant@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, peterz@...radead.org,
	oleg@...hat.com, hegdevasant@...ux.vnet.ibm.com, mingo@...hat.com,
	anton@...hat.com, systemtap@...rceware.org,
	aravinda@...ux.vnet.ibm.com, penberg@....fi
Subject: Re: Re: [PATCH v3 5/5] perf/sdt: Add support to perf record to
 trace SDT events

(2014/10/23 17:21), Namhyung Kim wrote:
> Hi Masami,
> 
> On Thu, 23 Oct 2014 15:33:37 +0900, Masami Hiramatsu wrote:
>> (2014/10/23 14:54), Srikar Dronamraju wrote:
>>> I am somehow not able to figure out how perf probe comes into the
>>> current workflow.
>>>
>>> I think the current design was
>>> 1. perf sdt-cache --add <file> (only once per file)
>>> 2. perf record -e <sdt-event>
>>>
>>> So what is the additional thing that perf probe does or Is it going to
>>> replace any of the above steps?
>>
>> 3. perf probe -a <sdt-event>
>>
>> And this will be done subsequently in this series (without user interface part).
>> However, current implementation of 2. will do the following steps
>>
>> s1. get sdt event data from sdt-cache
>> s2. set up sdt events with suppressing messages
>> s3. do recording events
>> (s4. and hiding existing sdt events from perf-probe --list)
>> s5. remove sdt events
>>
>> So, what I proposed were ;
>> - to implement s2., we can introduce --quiet(-q) option and use it
>>   instead of ->sdt flag checking
>> - removing s4. and s5.
>> - and add verification of existing sdt events at s2. if needed.
> 
> I'm okay with removing the s4 but not sure about the s5.  In that case,
> we might have many dynamic events in a system without noticing to users.

Indeed, okey, so let's keep s5 then :)

Thank you,

-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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