From owner-freebsd-current Fri Jan 31 11:55:46 2003 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 3813137B401 for ; Fri, 31 Jan 2003 11:55:45 -0800 (PST) Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2]) by mx1.FreeBSD.org (Postfix) with ESMTP id 7B98243F79 for ; Fri, 31 Jan 2003 11:55:44 -0800 (PST) (envelope-from dillon@apollo.backplane.com) Received: from apollo.backplane.com (localhost [127.0.0.1]) by apollo.backplane.com (8.12.6/8.12.6) with ESMTP id h0VJthSJ078663; Fri, 31 Jan 2003 11:55:43 -0800 (PST) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.12.6/8.12.6/Submit) id h0VJthKW078662; Fri, 31 Jan 2003 11:55:43 -0800 (PST) Date: Fri, 31 Jan 2003 11:55:43 -0800 (PST) From: Matthew Dillon Message-Id: <200301311955.h0VJthKW078662@apollo.backplane.com> To: Peter Wemm Cc: Bosko Milekic , "Daniel C. Sobral" , Trish Lynch , freebsd-current@FreeBSD.ORG Subject: Re: Hyperthreading and machdep.cpu_idle_hlt References: <20030131194817.335B72A89E@canning.wemm.org> Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG :The cache and most of the execution hardware is shared. The execution :units can run something like 4 instructions per clock. If the "idle" :logical core is in a spinloop, then it is generating instructions for :execution, so you are dividing the execution resources between one context :that is doing real work, and the other context that is burning off the :"excess" resources. Overall, it is a huge loss. It is absolutely essential :that logical cpus be halted when they are not doing useful work. Ah, that makes sense. Are the two logical cpus shared 50-50? -Matt :Cheers, :-Peter :-- :Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message