How to measure performance inside Kernel?

[Peter Senna Tschudin]

Hi Graeme,

I'm doing tests on Fedora 15 and using it's provided
/lib/modules/2.6.41.10-3.fc15.x86_64/build/Makefile for compiling the
module.

> For starters, I would not be surprised if the compiler produces identical
> code, and if not, code that has the same performance...

I've measured huge differences. Geometrical Mean of 512 values on Core i7:
Original_code:		98.2421756187
Proposed_code:		17.9710892854

> That sounds like a perfectly good methodology - It would be interesting to
> see how many reps are required before the mean settles down to a constant
> value - Maybe you don't need to run it so many times, or maybe you need to
>  run more...

During the run, measuring the original code reports some values that
are much higher than the average.
The graph is at: http://imgur.com/2WXAq

The full source of the module I'm using is at: http://goo.gl/cCMIa

What's wrong?

[]'s

Peter

-- 
Peter Senna Tschudin
peter.senna at gmail.com
gpg id: 48274C36