From owner-freebsd-questions@FreeBSD.ORG Sun Mar 27 20:51:09 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 D976B16A4CE for ; Sun, 27 Mar 2005 20:51:08 +0000 (GMT) Received: from out1.smtp.messagingengine.com (out1.smtp.messagingengine.com [66.111.4.25]) by mx1.FreeBSD.org (Postfix) with ESMTP id 6FCD743D54 for ; Sun, 27 Mar 2005 20:51:08 +0000 (GMT) (envelope-from list-freebsd-2004@morbius.sent.com) Received: from frontend3.messagingengine.com (frontend3.internal [10.202.2.152]) by frontend1.messagingengine.com (Postfix) with ESMTP id 3D8D2C63E14 for ; Sun, 27 Mar 2005 15:51:07 -0500 (EST) X-Sasl-enc: w3fMQovbdV8N+fJv0MWgVQ 1111956667 Received: from gumby.localhost (dsl-80-41-75-20.access.as9105.com [80.41.75.20]) by frontend3.messagingengine.com (Postfix) with ESMTP id 3AF67247F3 for ; Sun, 27 Mar 2005 15:51:07 -0500 (EST) From: RW To: freebsd-questions@freebsd.org Date: Sun, 27 Mar 2005 21:51:05 +0100 User-Agent: KMail/1.8 References: <8C7006AE7E80573-FAC-3B652@mblk-r28.sysops.aol.com> <49251524.20050326234521@wanadoo.fr> In-Reply-To: <49251524.20050326234521@wanadoo.fr> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200503272151.06216.list-freebsd-2004@morbius.sent.com> Subject: Re: hyper threading. X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 27 Mar 2005 20:51:09 -0000 On Saturday 26 March 2005 22:45, Anthony Atkielski wrote: > em1897@aol.com writes: > > Yes, the theory is very nice; you've done a nice > > job reading Intel's marketing garb. > > I haven't read their marketing materials. I'm simply going by the > technical descriptions I've read of the architecture. > > > However if you don't have a specific hyperthreading-aware scheduler > > and particularly well-written, threaded applications, you'll lose more > > than you'll gain. > > If that were true, then it would be equally true of systems with actual > multiple physical processors. In practice, multiple processors provide > an obvious performance gain, and hyperthreading does, too, although it's > much more modest than the gain obtained from physically independent > processors. The situation is very different. Multiple processors can run multiple processes at the same time. A HT processor can only run two threads from the same process. And most software isn't multithreaded.