linux-kernel - Re: [PATCH v4 2/3] Support for perf to probe into SDT markers:

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Date:	Fri, 25 Oct 2013 14:38:17 +0200
From:	Pekka Enberg <penberg@...nel.org>
To:	Hemant Kumar <hkshaw@...ux.vnet.ibm.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Oleg Nesterov <oleg@...hat.com>,
	hegdevasant@...ux.vnet.ibm.com, Ingo Molnar <mingo@...hat.com>,
	anton@...hat.com, systemtap@...rceware.org,
	Namhyung Kim <namhyung@...nel.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	aravinda@...ux.vnet.ibm.com
Subject: Re: [PATCH v4 2/3] Support for perf to probe into SDT markers:

Hello Hemant,

On Wed, Oct 23, 2013 at 7:05 AM, Hemant Kumar <hkshaw@...ux.vnet.ibm.com> wrote:
> This allows perf to probe into the sdt markers/notes present in
> the libraries and executables. We try to find the associated location
> and handle prelinking (since, stapsdt notes section is not allocated
> during runtime). Prelinking is handled with the help of base
> section which is allocated during runtime. This address can be compared
> with the address retrieved from the notes' description. If its different,
> we can take this difference and then add to the note's location.
>
> We can use existing '-a/--add' option to add events for sdt markers.
> Also, we can add multiple events at once using the same '-a' option.
>
> Usage:
> perf probe -x /lib64/libc.so.6 -a 'my_event=%libc:setjmp'
>
> Output:
> Added new event:
>   libc:my_event        (on 0x35981)
>
> You can now use it in all perf tools, such as:
>
>     perf record -e libc:my_event -aR sleep 1

Is there a technical reason why 'perf list' could not show all the
available SDT markers on a system and that the 'market to event'
mapping cannot happen automatically?

So instead of doing all the command line magic above I'd do:

  perf list

  libc:setjmp [SDT marker]

and I could just do

  perf record -e libc:setjmp -AR sleep 1

?

                    Pekka
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