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

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Message-ID: <54489298.3010108@linux.vnet.ibm.com>
Date:	Thu, 23 Oct 2014 11:01:04 +0530
From:	Hemant Kumar <hemant@...ux.vnet.ibm.com>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
CC:	linux-kernel@...r.kernel.org, srikar@...ux.vnet.ibm.com,
	peterz@...radead.org, oleg@...hat.com,
	hegdevasant@...ux.vnet.ibm.com, mingo@...hat.com, anton@...hat.com,
	systemtap@...rceware.org, namhyung@...nel.org,
	aravinda@...ux.vnet.ibm.com, penberg@....fi
Subject: Re: [PATCH v3 5/5] perf/sdt: Add support to perf record to trace
 SDT events


On 10/22/2014 03:11 PM, Masami Hiramatsu wrote:
> (2014/10/22 17:20), Hemant Kumar wrote:
>>>>  From "file_sdt_ent" we will find out the file name.
>>>> Convert this sdt note into a perf event and then write this into uprobe_events
>>>> file to be able to record the event.
>>>> Then, corresponding entries are added to uprobe_events file for
>>>> the SDT events.
>>>> After recording is done, these events are silently deleted from uprobe_events
>>>> file. The uprobe_events file is present in debugfs/tracing directory.
>>>>
>>>> To support the addition and deletion of SDT events to/from uprobe_events
>>>> file, a record_sdt struct is maintained which has the event data.
>>> OK, I have some comments on this.
>>>
>>>> An example usage:
>>>>
>>>> # ./perf record -e %user_app:fun_start -aR /home/user_app
>>> At first, I'd like to add SDT support for adding probes too, like below;
>>>
>>> ./perf probe -a '%user_app:fun_start $vars'
>> But I think, previously we discussed that we won't be having "perf
>> probe" for SDT events.
>> We list them and probe/trace them using "perf record" directly.
> Right, sorry for confusing you. I meant that I'd like to support SDT on both of
> perf-record and perf-probe :)

I plan to do this and add this subsequently but will it be okay if we go 
with the current
implementation for the time being?

What do you think?

> And even if we'll hide sdt related events via perf, users can access it via ftrace.
> So, I doubt that we can completely hide them, in that case, honesty is the best way;)
>
> Thank you,
>
>

-- 
Thanks,
Hemant Kumar

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