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

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Message-ID: <alpine.DEB.1.10.0811231455090.13888@gandalf.stny.rr.com>
Date:	Sun, 23 Nov 2008 14:56:42 -0500 (EST)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Andi Kleen <andi@...stfloor.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


On Sun, 23 Nov 2008, Andi Kleen wrote:
> Steven Rostedt <rostedt@...dmis.org> writes:

> > 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. 

I'd love to add an option that could hook into any arch with HW support 
for this. We could dump out the same information, but just a different way 
to gather it.  But I'm still ignorant to the use of CPU performance 
counters and how to find which branch matches which if.

-- Steve

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