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Subject: Re: [RFC][PATCH 0/2] tracing: Have trace_printk()s in the events/
 directory
From: Steven Rostedt <rostedt@goodmis.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Darren Hart <dvhart@linux.intel.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        "jason.wessel" <jason.wessel@windriver.com>,
        "Ted Ts'o" <tytso@mit.edu>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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References: <20101118035803.453609353@goodmis.org>
	 <1290076866.2109.1305.camel@laptop>
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Date: Thu, 18 Nov 2010 06:53:23 -0500
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On Thu, 2010-11-18 at 11:41 +0100, Peter Zijlstra wrote:
> On Wed, 2010-11-17 at 22:58 -0500, Steven Rostedt wrote:
> > For example, I added a trace_printk() in kernel/sched.c at line 2180
> > and it creates:
> > 
> > # ls /debug/tracing/events/printk/kernel/sched.c/2180/
> > enable  format
> > 
> > The format is the printk format:
> > 
> > # cat /debug/tracing/events/printk/kernel/sched.c/2180/format 
> > "migrate task %s:%d"
> 
> *groan*, so you're creating a tracepoint per instance?
> 
> That's going to be massive pain for perf.. I really don't see the point
> in splitting all that out.

a) The file directory was what was asked about in the referenced email.
b) This is just an example of a way to display it to the user, which
seems to be very intuitive.
c) Perf can implement the details anyway it wants. It can make a single
tracepoint callback and have the enabling of the points as a special
filter.
d) This was just an RFC that Frederic asked if I would do. I thought it
would be a fun challenge and did it. Let it bit rot in hell for all I
care, I wasn't taking it any further anyway.

-- Steve