linux-kernel - Re: [PATCH 01/17] perf util: Save pid-cmdline mapping into tracing header

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Message-ID: <20130731140746.GA3614@ghostprotocols.net>
Date:	Wed, 31 Jul 2013 11:07:46 -0300
From:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
To:	Namhyung Kim <namhyung.kim@....com>
Cc:	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>, David Ahern <dsahern@...il.com>,
	Stephane Eranian <eranian@...gle.com>,
	Jeremy Eder <jeder@...hat.com>
Subject: Re: [PATCH 01/17] perf util: Save pid-cmdline mapping into tracing
 header

Em Wed, Jul 31, 2013 at 09:51:54AM +0900, Namhyung Kim escreveu:
> 2013-07-30 오후 10:28, Arnaldo Carvalho de Melo 쓴 글:
> >Em Tue, Jul 30, 2013 at 06:18:58PM +0900, Namhyung Kim escreveu:
> >>Current trace info data lacks the saved cmdline mapping which is
> >>needed for pevent to find out the comm of a task.  Add this and bump
> >>up the version number so that perf can determine its presence when
> >>reading.

> >Can't we get this from the PERF_RECORD_COMM synthesized at the beginning
> >of the session + the kernel generated ones for new threads?

> >We would just call machine__find_thread() and use thread->comm, etc, no?

> Yes, I think it's doable.  However it needs an additional perf event
> only to generate the COMM events.  So I decided not to do it and

I don't think this is a problem, its in line with Ingo's suggestion of a
new perf ioctl to ask the kernel to generate PERF_RECORD_MMAP events for
existing threads.

- Arnaldo
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