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@gmail.com gpg id: 48274C36