From owner-freebsd-questions@FreeBSD.ORG Sun Mar 27 10:36:46 2005 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id C5E0A16A4CE for ; Sun, 27 Mar 2005 10:36:46 +0000 (GMT) Received: from smtp11.wanadoo.fr (smtp11.wanadoo.fr [193.252.22.31]) by mx1.FreeBSD.org (Postfix) with ESMTP id 749C843D2D for ; Sun, 27 Mar 2005 10:36:46 +0000 (GMT) (envelope-from atkielski.anthony@wanadoo.fr) Received: from me-wanadoo.net (localhost [127.0.0.1]) by mwinf1101.wanadoo.fr (SMTP Server) with ESMTP id A19AF1C000C6 for ; Sun, 27 Mar 2005 12:36:45 +0200 (CEST) Received: from pix.atkielski.com (ASt-Lambert-111-2-1-3.w81-50.abo.wanadoo.fr [81.50.80.3]) by mwinf1101.wanadoo.fr (SMTP Server) with ESMTP id 7C2F41C000A4 for ; Sun, 27 Mar 2005 12:36:45 +0200 (CEST) X-ME-UUID: 20050327103645509.7C2F41C000A4@mwinf1101.wanadoo.fr Date: Sun, 27 Mar 2005 12:36:45 +0200 From: Anthony Atkielski X-Priority: 3 (Normal) Message-ID: <467157066.20050327123645@wanadoo.fr> To: freebsd-questions@freebsd.org In-Reply-To: <8C700841A4F8661-A38-3B468@mblk-r33.sysops.aol.com> References: <1641928994.20050326192811@wanadoo.fr> <8C700529A2DFD74-A44-3A157@mblk-d34.sysops.aol.com> <439876144.20050326220638@wanadoo.fr> <8C7006AE7E80573-FAC-3B652@mblk-r28.sysops.aol.com> <49251524.20050326234521@wanadoo.fr> <8C7007D5D4D30D2-A38-3B313@mblk-r33.sysops.aol.com> <42460B1C.1050008@cloudview.com> <8C700841A4F8661-A38-3B468@mblk-r33.sysops.aol.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Subject: Re: hyper threading. X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list Reply-To: freebsd-questions@freebsd.org List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 27 Mar 2005 10:36:46 -0000 em1897@aol.com writes: > When you get your machine running without a kernel > let me know. The kernel is the key to the O/S. If you > don't need networking and don't have many interrupts, > then it probably doesnt matter that much. The kernel represents only a small part of total system utilization and throughput. Even if everything is single-threaded through the kernel, you can still get performance benefits from multiple processors, because they can run userland processes in parallel. If total system load is 5% kernel and 80% userland in a UP environment, and moving to a MP environment doubles kernel overhead, total system load has still increased by only 5%. In general, many things must be single-threaded through the kernel because of the need for proper synchronization. Thus, the kernel always shows more negative effects from MP than the system as a whole, but since it is so small in the overall picture, MP still improves global performance. -- Anthony