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Date: Fri, 30 Nov 2007 10:01:49 +0100
From: Kris Kennaway <kris@FreeBSD.org>
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To: Claus Guttesen <kometen@gmail.com>
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Cc: max@love2party.net, freebsd-stable@freebsd.org,
	Pete French <petefrench@ticketswitch.com>
Subject: Re: Also seeing 2 x quad-core system slower that 2 x dual core
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Claus Guttesen wrote:
>> Thing is that GENERIC as installed out of the box should not take two minutes
>> to delete a gig of files off a 15k RPM SAS drive! especially not
>> when identical hardware with half the number of processor cores only takes
>> eleven seconds to do the same job. Something is wrong somewhere if doubling
>> your CPU's results in a factor of 12 slowdown surely?
> 
> Is it possible to disable one of the quad-core cpu's from bios? I have
> a couple of DL360's myself but I haven't had the need to disable one
> of the cpu's.
> 
> If so it could be interesting to see whether the specific task goes
> slower/faster.

Yes, if the claim is that the hardware is absolutely identical apart 
from one having two quad-core CPUs instead of two dual-core, the next 
step is to disable half of the CPUs and confirm that the problem goes away.

Check dmesg for the APIC numbers corresponding to the CPUs you want to 
disable and add the corresponding entries to /boot/loader.conf, e.g.:

hint.lapic.1.disable="1"
hint.lapic.3.disable="1"
hint.lapic.5.disable="1"
hint.lapic.7.disable="1"

Kris