linux-kernel - Re: [PATCH] i386-pda UP optimization

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Date:	Wed, 15 Nov 2006 12:32:31 +0100
From:	Andi Kleen <ak@...e.de>
To:	Eric Dumazet <dada1@...mosbay.com>
Cc:	akpm@...l.org, Arjan van de Ven <arjan@...radead.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>, mingo@...e.hu,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i386-pda UP optimization

On Wednesday 15 November 2006 12:27, Eric Dumazet wrote:
> Seeing %gs prefixes used now by i386 port, I recalled seeing strange oprofile 
> results on Opteron machines.
> 
> I really think %gs prefixes can be expensive in some (most ?) cases, even if 
> the Intel/AMD docs say they are free.

They aren't free, just very cheap.

> 
> With the attached patch, I got 12.212 s, and a kernel text size reduction of 
> 3400 bytes.

Are the benchmark numbers stable? i.e. if you repeat them multiple times
with reboots do you still get the same difference?

-Andi
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