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Date: Thu, 11 Sep 2003 18:48:39 +0100
From: Jamie Lokier <jamie@shareable.org>
To: Andi Kleen <ak@suse.de>
Cc: richard.brunner@amd.com, linux-kernel@vger.kernel.org, akpm@osdl.org,
       torvalds@osdl.org
Subject: Re: [PATCH] 2.6 workaround for Athlon/Opteron prefetch errata
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References: <99F2150714F93F448942F9A9F112634C0638B196@txexmtae.amd.com> <20030911012708.GD3134@wotan.suse.de> <20030911165845.GE29532@mail.jlokier.co.uk> <20030911190516.64128fe9.ak@suse.de> <20030911173245.GJ29532@mail.jlokier.co.uk> <20030911193954.63724a82.ak@suse.de>
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Andi Kleen wrote:
> signal exception path is thousands of cycles, we're talking about tens
> of cycles here.

<hand-waving>

Tens vs thousands == percentage points.

Isn't it about 20 cycles per mispredicted branch on a P4?

Five of those and we're talking several percent slowdown, ridiculous
as it seems.

</hand-waving>

-- Jamie