Date: Fri, 29 Aug 2003 12:03:48 +0200
From: "J.A. Magallon" <jamagallon@able.es>
To: Jamie Lokier <jamie@shareable.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: x86, ARM, PARISC, PPC, MIPS and Sparc folks please run this
Message-ID: <20030829100348.GA5417@werewolf.able.es>
References: <20030829053510.GA12663@mail.jlokier.co.uk>
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On 08.29, Jamie Lokier wrote:
> Dear All,
[...]
> 
> I already got a surprise (to me): my Athlon MP is much slower
> accessing multiple mappings which are within 32k of each other, than
> mappings which are further apart, although it is coherent.  The L1
> data cache is 64k.  (The explanation is easy: virtually indexed,
> physically tagged cache moves data among cache lines, possibly via L2).
> 

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...)

-- 
J.A. Magallon <jamagallon@able.es>      \                 Software is like sex:
werewolf.able.es                         \           It's better when it's free
Mandrake Linux release 9.2 (Cooker) for i586
Linux 2.4.22-jam1m (gcc 3.3.1 (Mandrake Linux 9.2 3.3.1-1mdk))
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