From owner-freebsd-current@FreeBSD.ORG  Thu May  7 08:39:38 2009
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From: Bob Bishop <rb@gid.co.uk>
To: pluknet <pluknet@gmail.com>
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Date: Thu, 7 May 2009 09:17:15 +0100
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Cc: Barney Cordoba <barney_cordoba@yahoo.com>,
	"Current@freebsd.org" <Current@freebsd.org>
Subject: Re: Hypertherading
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Hi,

On 7 May 2009, at 03:55, pluknet wrote:

> 2009/5/7 Barney Cordoba <barney_cordoba@yahoo.com>:
>>
>> I just got a shiny new nehalem box and it comes up with 16  
>> processors with dual quads installed. Is there any benefit or  
>> should hyperthreading be disabled?
>>
>
> Hi. There is a measurable win if hyperthreading is enabled [1].

AFAICS the reference doesn't support that conclusion at all.

> You can switch it off via machdep.hyperthreading_enabled loader  
> tunable.
>
> [1] http://lists.freebsd.org/pipermail/freebsd-stable/2009-January/047460.html

--
Bob Bishop
rb@gid.co.uk