From owner-freebsd-hackers@FreeBSD.ORG  Thu Apr  1 03:01:21 2004
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
Delivered-To: freebsd-hackers@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 44AAC16A4CE
	for <freebsd-hackers@freebsd.org>;
	Thu,  1 Apr 2004 03:01:21 -0800 (PST)
Received: from tx2.oucs.ox.ac.uk (tx2.oucs.ox.ac.uk [163.1.2.163])
	by mx1.FreeBSD.org (Postfix) with ESMTP id BF8E643D3F
	for <freebsd-hackers@freebsd.org>;
	Thu,  1 Apr 2004 03:01:20 -0800 (PST)
	(envelope-from colin.percival@wadham.ox.ac.uk)
Received: from scan2.oucs.ox.ac.uk ([163.1.2.162] helo=localhost)
	by tx2.oucs.ox.ac.uk with esmtp (Exim 4.24)
	id 1B8zwl-0006dy-Lq
	for freebsd-hackers@freebsd.org; Thu, 01 Apr 2004 12:01:19 +0100
Received: from rx2.oucs.ox.ac.uk ([163.1.2.161])
 by localhost (scan2.oucs.ox.ac.uk [163.1.2.162]) (amavisd-new, port 25)
 with ESMTP id 25235-07 for <freebsd-hackers@freebsd.org>;
 Thu,  1 Apr 2004 12:01:19 +0100 (BST)
Received: from gateway.wadham.ox.ac.uk ([163.1.161.253])
	by rx2.oucs.ox.ac.uk with smtp (Exim 4.24)
	id 1B8zwl-0006ds-8P
	for freebsd-hackers@freebsd.org; Thu, 01 Apr 2004 12:01:19 +0100
Received: (qmail 3609 invoked by uid 1004); 1 Apr 2004 11:01:19 -0000
Received: from colin.percival@wadham.ox.ac.uk by gateway by uid 71 with
	qmail-scanner-1.20 
	(clamscan: 0.67. sweep: 2.18/3.79.  Clear:RC:1(163.1.161.131):. 
	Processed in 0.042936 secs); 01 Apr 2004 11:01:19 -0000
Received: from dhcp1131.wadham.ox.ac.uk (HELO piii600.wadham.ox.ac.uk)
	(163.1.161.131)
	by gateway.wadham.ox.ac.uk with SMTP; 1 Apr 2004 11:01:19 -0000
Message-Id: <6.0.1.1.1.20040401115446.0378a8f8@imap.sfu.ca>
X-Sender: cperciva@imap.sfu.ca (Unverified)
X-Mailer: QUALCOMM Windows Eudora Version 6.0.1.1
Date: Thu, 01 Apr 2004 12:01:15 +0100
To: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net>
From: Colin Percival <colin.percival@wadham.ox.ac.uk>
In-Reply-To: <Pine.BSF.4.53.0404010704010.15681@e0-0.zab2.int.zabbadoz.n
 et>
References: <Pine.BSF.4.53.0404010704010.15681@e0-0.zab2.int.zabbadoz.net>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
cc: freebsd-hackers@freebsd.org
Subject: Re: implications of SMP kernel on UP
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
	<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 01 Apr 2004 11:01:21 -0000

At 08:10 01/04/2004, Bjoern A. Zeeb wrote:
>what are the implications on running an SMP enabled kernel on a UP
>machine ?
>
>I first thought of things like:
>- performence (most likely not worth the discussion ?)

  At least in 5.2-RELEASE, there is a significant performance
delta; buildworld takes about 5% longer on an SMP kernel (and
the time spent in the kernel is 20% longer).
  I know some optimizations were done shortly after 5.2, so I
wouldn't be surprised if this situation has improved.

Colin Percival