linux-kernel - Re: request to add trace off and trace on with events

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Message-ID: <1271715227.10448.145.camel@gandalf.stny.rr.com>
Date:	Mon, 19 Apr 2010 18:13:47 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Tim Bird <tim.bird@...sony.com>, Tom Zanussi <tzanussi@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Chase Douglas <chase.douglas@...onical.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: request to add trace off and trace on with events

On Tue, 2010-04-20 at 00:04 +0200, Frederic Weisbecker wrote:
> On Mon, Apr 19, 2010 at 05:37:54PM -0400, Steven Rostedt wrote:

> > # cat event/sched/sched_switch/triggers/tracing_off
> > disabled
> > 
> > Or it can be a filter, or enabled.
> 
> 
> Yep, since it would share exatly the same code than filter (as
> filter basically becomes a trigger command), it can behave the
> same: displaying "none" when there is no filter, or a filter.
> 

Then do we make the triggers themselves directories too?

# ls event/sched/sched_switch/triggers/tracing_off
filter   enable

?

> 
> > 
> > This could also allow a user to do:
> > 
> > echo "(a > 100)" > tracing_on
> > echo "(a < 100)" > tracing_off
> 
> 
> Yeah :)
> But if the scope of the "tracing off" is only for this event, then
> rather use:
> 
> echo "(a < 100)" > filter
> 
> You could have tracing_off/on that have this event scope and
> tracing_off/on_all for a global tracing scope.

The two are not equivalent. In fact, just enabling a trigger does not
mean that the event itself will be traced.

-- Steve


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