Subject: Re: x86, ARM, PARISC, PPC, MIPS and Sparc folks please run this
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: "J.A. Magallon" <jamagallon@able.es>
Cc: Jamie Lokier <jamie@shareable.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
In-Reply-To: <20030829100348.GA5417@werewolf.able.es>
References: <20030829053510.GA12663@mail.jlokier.co.uk>
	 <20030829100348.GA5417@werewolf.able.es>
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Date: 29 Aug 2003 11:36:31 +0100
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On Gwe, 2003-08-29 at 11:03, J.A. Magallon wrote:
> Sorry if this is a stupid question, but have you heard about 64K-aliasing ?
> We have seen it in P3/P4, do not know if Athlons also suffer it.
> In short, x86 is crap. It slows like a dog when accessing two memory
> positions sparated by 2^n (address decoder has two 16 bits adders, instead
> of 1 32 bits..., cache is 16 bit tagged, etc...)

Pretty much all processors are bad at handling memory accesses on the
same alignment within powers of two. Thats one of the reasons for slab
and for things like the old kernel code putting skb structs at the end
of the skbuff data.

Grab a copy of "Unix systems for modern architectures".


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