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

From: Namhyung Kim <namhyung@kernel.org>
To: David Ahern <dsahern@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@kernel.org>,
	Namhyung Kim <namhyung.kim@lge.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Jiri Olsa <jolsa@redhat.com>,
	Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 06/19] perf ftrace: Add support for --pid option
Date: Thu, 27 Jun 2013 23:12:52 +0900	[thread overview]
Message-ID: <1372342372.1734.6.camel@leonhard> (raw)
In-Reply-To: <51CC44A9.60809@gmail.com>

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