Subject: Re: [RFC][PATCH 1/2 v2] tracing: Add TRACE_EVENT_CONDITIONAL()
From: Steven Rostedt <rostedt@goodmis.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Theodore Tso <tytso@mit.edu>, Arjan van de Ven <arjan@infradead.org>
In-Reply-To: <20101203152733.GA25580@Krystal>
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	 <20101203152733.GA25580@Krystal>
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Date: Fri, 03 Dec 2010 10:38:47 -0500
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On Fri, 2010-12-03 at 10:27 -0500, Mathieu Desnoyers wrote:

> > >   TP_CONDITION(unlikely(someparam)),
> > 
> > I actually think this is an abuse of "unlikely".
> 
> Why are you considering this an abuse ?

Because it is overused. I would rather get rid of most unlikely()'s
because they are mostly meaningless. Just run the unlikely profiler, and
you will see a large number of them are just plain incorrect.

Adding them here probably doesn't do any good. The only reason for this
TP_CONDITION() is to ignore those cases that it just does not make sense
to trace. Like a wake up tracepoint that does not wake anything up. No
need for "unlikely" or "likely", by trying to do that, you will most
likely get it wrong.

	unlikely(use_likely_correctly)


-- Steve


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