linux-kernel - Re: [PATCH] expand micro-optimizations in kernel to newer model CPUs

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Date:	Sun, 15 Dec 2013 04:42:50 -0800 (PST)
From:	John <da_audiophile@...oo.com>
To:	Richard Weinberger <richard.weinberger@...il.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"david.heidelberger@...t.cz" <david.heidelberger@...t.cz>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] expand micro-optimizations in kernel to newer model CPUs





----- Original Message -----
> From: Richard Weinberger <>
>
> A *very* small speedup.
> 
> And I really doubt your numbers.
> Why are you using ANOVA? You're comparing *two* groups not more than two.
> I had a quick look at your raw numbers, they don't seem to be normally
> distributed at all.
> Did you remove some peaks?
> 


Hi Richard.  Thank you for your interest.  Yes, a small speedup as I mentioned but  I'll note that the current kernel code includes the MCORE2 option.  I tested this against some of the newer ones and they are all on par with each other.  For example, here are differences in median values:

CPUDifference in median value
core2        +87.5 ms
core7-avx+79.7 ms
core-avx-i+257.2 ms

I am using ANOVA to establish that the generic group differs from the optimized group.  I have always used ANOVA for this sort of comparison whether using two or more groups.  In fact, thumb through any medical or scientific journal, you'll see others in pier reviewed article doing the same.  

I did not remove any datapoints; I do not understand why you don't think the sets are normally distributed.  Did you see the normal quantile plots?  Additionally, the population variances are fairly equal (Levene and Barlett tests). 
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