linux-kernel - Re: [PATCH 4/4] trace: profile all if conditionals

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Message-ID: <87iqqei5ys.fsf@basil.nowhere.org>
Date:	Sun, 23 Nov 2008 20:43:07 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Theodore Tso <tytso@....edu>,
	Arjan van de Ven <arjan@...radead.org>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH 4/4] trace: profile all if conditionals

Steven Rostedt <rostedt@...dmis.org> writes:
>
> Miss means the branch was not taken. Hit means the branch was taken.
> The percent is the percentage the branch was taken.

I'm not sure the results are very useful? What would
you do with it?

It seems like a very special case of gcov, but I think I would
rather have the full thing (patches in -mm I think)

> This adds a significant amount of overhead and should only be used
> by those analyzing their system.

Often this can be also done using CPU performance counters. Might 
be a cheaper option. 

-Andi

-- 
ak@...ux.intel.com
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