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Re: [PATCH 1/2] SDT markers listing by perf
- From: Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>
- To: Hemant <hkshaw at linux dot vnet dot ibm dot com>
- Cc: Namhyung Kim <namhyung at kernel dot org>, linux-kernel at vger dot kernel dot org, srikar at linux dot vnet dot ibm dot com, peterz at infradead dot org, oleg at redhat dot com, mingo at redhat dot com, anton at redhat dot com, systemtap at sourceware dot org
- Date: Wed, 25 Sep 2013 17:45:23 +0900
- Subject: Re: [PATCH 1/2] SDT markers listing by perf
- Authentication-results: sourceware.org; auth=none
- References: <20130903072944 dot 4793 dot 93584 dot stgit at hemant-fedora> <20130903073655 dot 4793 dot 20013 dot stgit at hemant-fedora> <87ioyht7e4 dot fsf at sejong dot aot dot lge dot com> <5226E8F4 dot 5060505 at hitachi dot com> <523599C2 dot 6020204 at linux dot vnet dot ibm dot com> <5242687A dot 9030209 at hitachi dot com> <52427CAE dot 8030600 at linux dot vnet dot ibm dot com>
(2013/09/25 15:03), Hemant wrote:
>>> I have one doubt here. Why do we need [ARG ...] in the syntax you
>>> specified? I believe these args are to fetched from the sdt notes'
>>> section of the elf of the executable/library. Or am I taking this in a
>>> wrong way and this suggested syntax is actually for the uprobe_events
>>> file in the tracing directory?
>> Hm, indeed. Since all the arguments of the marker is defined in sdt notes,
>> we actually don't need to specify each of them. However, other probe syntax
>> has those arguments. I'd like to keep the same syntax style in the
>> same command (action) for avoiding confusion.
>
> Hmm, got it.
>
>> I recommend this way; at the first step, we just find the marker address from
>> sdt. And next, we will make the argument available. And eventually,
>> it is better to introduce "$args" meta argument to fetch all the arguments
>> of the marker.
>>
>> At this point, we can do
>>
>> perf probe %foo:bar $args
>
> So, at first step (ignoring the arguments), we can go with :
> perf probe %foo:bar
Right,
> And, once, the argument support is enabled (all the arguments will be
> fetched at the marker location), we can go with:
> perf probe %foo:bar $args
Correct ;). In my plan, $parms and $vars will be also introduced for
accessing all function parameters and local variables correspondingly.
Thank you!
--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com