From owner-freebsd-questions@FreeBSD.ORG Thu Jan 13 21:05:29 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 E864216A4D6 for ; Thu, 13 Jan 2005 21:05:29 +0000 (GMT) Received: from smtp7.wanadoo.fr (smtp7.wanadoo.fr [193.252.22.24]) by mx1.FreeBSD.org (Postfix) with ESMTP id 8ABF343D5C for ; Thu, 13 Jan 2005 21:05:23 +0000 (GMT) (envelope-from atkielski.anthony@wanadoo.fr) Received: from me-wanadoo.net (localhost [127.0.0.1]) by mwinf0707.wanadoo.fr (SMTP Server) with ESMTP id 6EA8F18000B3 for ; Thu, 13 Jan 2005 22:05:22 +0100 (CET) Received: from pix.atkielski.com (ASt-Lambert-111-2-1-3.w81-50.abo.wanadoo.fr [81.50.80.3]) by mwinf0707.wanadoo.fr (SMTP Server) with ESMTP id 4EAB118000AD for ; Thu, 13 Jan 2005 22:05:22 +0100 (CET) Date: Thu, 13 Jan 2005 22:05:22 +0100 From: Anthony Atkielski X-Priority: 3 (Normal) Message-ID: <1345467628.20050113220522@wanadoo.fr> To: freebsd-questions@freebsd.org In-Reply-To: <41E6DC30.3040501@netfence.it> References: <200501121049.j0CAnJQe028309@mp.cs.niu.edu> <828997113.20050112184556@wanadoo.fr> <41E58E53.7060606@netfence.it> <786252184.20050113014354@wanadoo.fr> <41E65688.4010700@netfence.it> <1242214203.20050113205210@wanadoo.fr> <41E6DC30.3040501@netfence.it> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Subject: Re: Hyperthreading hurts 5.3? 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: Thu, 13 Jan 2005 21:05:30 -0000 Andrea Venturoli writes: AV> I've come to the same conclusion. Still I can't put this together with AV> 100% load on both processors. If, as someone said, there is only one AV> FPU, *how* are these figures coming out??? The operating system tracks a dispatch of a processor into a process thread. After that, it has no idea whether the processor is actually doing anything or not--from the OS' standpoint, the processor is "running." So if one thread in one logical processor is actually executing instructions, and the other is stalled while waiting for a shared resource in the processor, the OS will still consider both threads to be "running" and will charge all of the elapsed time as processor time ... giving you a figure of 100% busy. AV> I would have expected something like 50%-50% (instead of 100%-0% of AV> the single threaded version). *If* there is only one FPU, I'd expect AV> both virtual processors being frequently idle waiting for each AV> other. Yes ... but the OS can't see that, and so OS monitoring tools can't report it. -- Anthony