linux-kernel - Re: [PATCH 06/19] perf ftrace: Add support for --pid option

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Date:	Thu, 27 Jun 2013 23:12:52 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	David Ahern <dsahern@...il.com>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 06/19] perf ftrace: Add support for --pid option

2013-06-27 (목), 07:56 -0600, David Ahern:
> On 6/26/13 11:23 PM, Namhyung Kim wrote:
> > The pid filtering in ftrace is done via set_ftrace_pid file under the
> > tracing debugfs directory.  IIRC It only supports process filtering not
> > thread filtering by iterating all threads in the kernel code.  So --tid
> > option cannot be implemented as other perf commands.
> >
> > So I chose not to and assigned -t option to --tracer.
> 
> Could that ever change? With the current code why call it pid in the 
> option but assign it to target.tid? Seems a like a source for confusion 

Hmm.. right.  I did it in order not to do same iteration of the thread
group in user space.  But now I think that it's just an unnecessary
optimization and can confuse readers.


> later. Would be better to just assign to target.pid and let the 
> machinery do the right thing.

Will do.

Thanks,
Namhyung


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