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From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 2/4] tracing: add event trace infrastructure
Date: Wed, 25 Feb 2009 15:24:35 +1100
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Cc: Andrew Morton <akpm@linux-foundation.org>,
       LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
       Thomas Gleixner <tglx@linutronix.de>,
       Peter Zijlstra <peterz@infradead.org>,
       Frederic Weisbecker <fweisbec@gmail.com>, Theodore Tso <tytso@mit.edu>,
       Arjan van de Ven <arjan@infradead.org>, Pekka Paalanen <pq@iki.fi>,
       Arnaldo Carvalho de Melo <acme@redhat.com>,
       Jason Baron <jbaron@redhat.com>, Martin Bligh <mbligh@google.com>,
       Mathieu Desnoyers <compudj@krystal.dyndns.org>,
       "Frank Ch. Eigler" <fche@redhat.com>,
       KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       Jens Axboe <jens.axboe@oracle.com>,
       Masami Hiramatsu <mhiramat@redhat.com>,
       Steven Rostedt <srostedt@redhat.com>
References: <20090225025608.956691460@goodmis.org> <20090224194548.3effb746.akpm@linux-foundation.org> <alpine.DEB.2.00.0902242252480.12697@gandalf.stny.rr.com>
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On Wednesday 25 February 2009 15:08:56 Steven Rostedt wrote:
> On Tue, 24 Feb 2009, Andrew Morton wrote:
> > On Tue, 24 Feb 2009 21:56:10 -0500 Steven Rostedt <rostedt@goodmis.org> 
wrote:
> > > From: Steven Rostedt <srostedt@redhat.com>
> > >
> > > This patch creates the event tracing infrastructure of ftrace.
> > > It will create the files:
> > >
> > >  /debug/tracing/available_events
> > >  /debug/tracing/set_event
> > >
> > > The available_events will list the trace points that have been
> > > registered with the event tracer.
> > >
> > > set_events will allow the user to enable or disable an event hook.
> > >
> > > example:
> > >
> > >  # echo sched_wakeup > /debug/tracing/set_event
> > >
> > > Will enable the sched_wakeup event (if it is registered).
> > >
> > >  # echo "!sched_wakeup" >> /debug/tracing/set_event
> > >
> > > Will disable the sched_wakeup event (and only that event).
> >
> > Why not
> >
> > echo sched_wakeup > /debug/tracing/set_event
> > echo sched_wakeup > /debug/tracing/clear_event
>
> I'm trying to keep the number of files in /debug/tracing down.

Why? Andrew's proposal is much cleaner. (what is the !sched_wakeup
event? An event you get when the scheduler does not wake up a task? ;)