linux-kernel - Re: [PATCH 1/2 v2][RFC] trace: profile likely and unlikely annotations

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Message-ID: <20081029094058.50bdaa4b@infradead.org>
Date:	Wed, 29 Oct 2008 09:40:58 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, Theodore Tso <tytso@....edu>,
	Mike Snitzer <snitzer@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Daniel Walker <dwalker@...sta.com>
Subject: Re: [PATCH 1/2 v2][RFC] trace: profile likely and unlikely
 annotations

On Wed, 29 Oct 2008 12:35:44 -0400 (EDT)
Steven Rostedt <rostedt@...dmis.org> wrote:

> 
> Andrew Morton recently suggested having an in-kernel way to profile
> likely and unlikely macros. This patch achieves that goal.
> 
> When configured, every(*) likely and unlikely macro gets a counter
> attached to it. When the condition is hit, the hit and misses of that
> condition are recorded. These numbers can later be retrieved by:
> 
>   /debugfs/tracing/profile_likely    - All likely markers
>   /debugfs/tracing/profile_unlikely  - All unlikely markers.
> 

I like the general approach
it'd be very convenient if the debugfs files also had a
percentage-incorrect (or percentage-correct, either way) listed,
so that we humans can focus straight on which ones are outliers rather
than having to do math in our heads first...


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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