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Re: [PATCH v4 2/3] Support for perf to probe into SDT markers:
- From: Pekka Enberg <penberg at kernel dot org>
- To: Hemant Kumar <hkshaw at linux dot vnet dot ibm dot com>
- Cc: LKML <linux-kernel at vger dot kernel dot org>, Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>, Peter Zijlstra <peterz at infradead dot org>, Oleg Nesterov <oleg at redhat dot com>, hegdevasant at linux dot vnet dot ibm dot com, Ingo Molnar <mingo at redhat dot com>, anton at redhat dot com, systemtap at sourceware dot org, Namhyung Kim <namhyung at kernel dot org>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, aravinda at linux dot vnet dot ibm dot com
- Date: Fri, 25 Oct 2013 14:38:17 +0200
- Subject: Re: [PATCH v4 2/3] Support for perf to probe into SDT markers:
- Authentication-results: sourceware.org; auth=none
- References: <20131023044511 dot 1886 dot 82571 dot stgit at hemant-fedora> <20131023050502 dot 1886 dot 15779 dot stgit at hemant-fedora>
Hello Hemant,
On Wed, Oct 23, 2013 at 7:05 AM, Hemant Kumar <hkshaw@linux.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