From owner-freebsd-hardware@FreeBSD.ORG  Thu Oct  2 10:21:45 2003
Return-Path: <owner-freebsd-hardware@FreeBSD.ORG>
Delivered-To: freebsd-hardware@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 4AEEA16A4B3
	for <hardware@freebsd.org>; Thu,  2 Oct 2003 10:21:45 -0700 (PDT)
Received: from ganymede.hub.org (u173n10.eastlink.ca [24.224.173.10])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 0468643FBF
	for <hardware@freebsd.org>; Thu,  2 Oct 2003 10:21:41 -0700 (PDT)
	(envelope-from scrappy@hub.org)
Received: by ganymede.hub.org (Postfix, from userid 1000)
	id B75163443F; Thu,  2 Oct 2003 14:20:48 -0300 (ADT)
Received: from localhost (localhost [127.0.0.1])
	by ganymede.hub.org (Postfix) with ESMTP
	id B5A6E3442F; Thu,  2 Oct 2003 14:20:48 -0300 (ADT)
Date: Thu, 2 Oct 2003 14:20:48 -0300 (ADT)
From: "Marc G. Fournier" <scrappy@hub.org>
To: Damian Gerow <damian@sentex.net>
In-Reply-To: <20031002170952.GF15256@sentex.net>
Message-ID: <20031002141921.K25730@ganymede.hub.org>
References: <200310021105.10872.john@johnrshannon.com>
	<20031002170952.GF15256@sentex.net>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
cc: hardware@freebsd.org
Subject: Re: Hyperthreading Kernel Configuration - 5.1
X-BeenThere: freebsd-hardware@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: General discussion of FreeBSD hardware
	<freebsd-hardware.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hardware>,
	<mailto:freebsd-hardware-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hardware>
List-Post: <mailto:freebsd-hardware@freebsd.org>
List-Help: <mailto:freebsd-hardware-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hardware>,
	<mailto:freebsd-hardware-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 02 Oct 2003 17:21:45 -0000



On Thu, 2 Oct 2003, Damian Gerow wrote:

> Thus spake John R. Shannon (john@johnrshannon.com) [02/10/03 13:05]:
> > On a new computer, dmesg shows:
> >
> > CPU: Intel(R) Pentium(R) 4 CPU 2.80GHz (2793.01-MHz 686-class CPU)
> >   Origin = "GenuineIntel"  Id = 0xf29  Stepping = 9
> >   Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
> >   Hyperthreading: 2 logical CPUs
> > acpi_cpu0: <CPU> port 0x530-0x537 on acpi0
> > acpi_cpu1: <CPU> port 0x530-0x537 on acpi0
> >
> > Should options  SMP  and  APIC_IO  be enabled in kernel?
>
> In short: yes.  And then you need to look at the machdep.* sysctl nobs,
> there's one you need to enable in there (I've forgotten which one).
>
> But that leads me to a secondary question: is enabling HTT really worth the
> time?  I know that people have said that using HTT can actually make your
> system slower -- is this an implementation issue, or did Intel really
> release something that degrades performance?

My understanding is that the speed improvements (or degradation) depend on
the use of the machine ... for instance, I've heard that a high I/O server
will be slower with HTT enabled, and, from my experience with one such, it
is so ... I'm not sure what circumstances would show improvements though
...