From owner-freebsd-current@FreeBSD.ORG  Mon Nov 15 04:06:28 2004
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: freebsd-current@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id C2F3C16A4D6
	for <current@freebsd.org>; Mon, 15 Nov 2004 04:06:28 +0000 (GMT)
Received: from pooker.samsco.org (pooker.samsco.org [168.103.85.57])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 57A1143D48
	for <current@freebsd.org>; Mon, 15 Nov 2004 04:06:28 +0000 (GMT)
	(envelope-from scottl@freebsd.org)
Received: from [192.168.254.11] (junior-wifi.samsco.home [192.168.254.11])
	(authenticated bits=0)
	by pooker.samsco.org (8.12.11/8.12.10) with ESMTP id iAF48NUd016658;
	Sun, 14 Nov 2004 21:08:23 -0700 (MST)
	(envelope-from scottl@freebsd.org)
Message-ID: <41982B70.4020508@freebsd.org>
Date: Sun, 14 Nov 2004 21:07:12 -0700
From: Scott Long <scottl@freebsd.org>
User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.7.2) Gecko/20040929
X-Accept-Language: en-us, en
MIME-Version: 1.0
To: "Wilkinson, Alex" <alex.wilkinson@dsto.defence.gov.au>
References: <4197C217-3622-11D9-B78A-000A95A9A574@nordahl.net>
	<41972BA2.3090609@freebsd.org>     <d8a0b76204111402012a63fcff@mail.gmail.com>
	<4197A47D.1070205@freebsd.org>
	<4487F0CE-3685-11D9-B78A-000A95A9A574@nordahl.net>
	<d8a0b76204111418561b49921d@mail.gmail.com>
	<20041115034101.GF51636@squash.dsto.defence.gov.au>
In-Reply-To: <20041115034101.GF51636@squash.dsto.defence.gov.au>
X-Enigmail-Version: 0.86.1.0
X-Enigmail-Supports: pgp-inline, pgp-mime
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
X-Spam-Status: No, hits=0.0 required=3.8 tests=none autolearn=no version=2.63
X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on pooker.samsco.org
cc: current@freebsd.org
Subject: Re: Detection of HTT
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 15 Nov 2004 04:06:28 -0000

Wilkinson, Alex wrote:
> Why is HTT turned off out of the box ? I thought HTT was meant to be a
> hardware 'performance enhancing' feature.
> 
> Why do we disable it ?
> 
>  - aW

FreeBSD will use HTT if the system has it enabled (usually controlled in
the BIOS) and the kernel is compiled for SMP.  There are ways to
manually disable HTT but leave SMP enabled in the OS, but the default is
to use it if the above two requirements are met.  However, the OS
scheduler is not HTT-aware, so HTT will give a somewhat mixed
performance.

Scott