Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264810AbTFLNus (ORCPT ); Thu, 12 Jun 2003 09:50:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264826AbTFLNus (ORCPT ); Thu, 12 Jun 2003 09:50:48 -0400 Received: from lvs01-fl.valueweb.net ([216.219.253.200]:47746 "EHLO ams003.ftl.affinity.com") by vger.kernel.org with ESMTP id S264810AbTFLNum (ORCPT ); Thu, 12 Jun 2003 09:50:42 -0400 Message-ID: <3EE887FA.90008@coyotegulch.com> Date: Thu, 12 Jun 2003 10:02:34 -0400 From: Scott Robert Ladd User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3.1) Gecko/20030527 Debian/1.3.1-2 X-Accept-Language: en MIME-Version: 1.0 To: "J.A. Magallon" CC: Artemio , Linux Kernel Mailing List Subject: Re: SMP question References: <200306112313.30903.artemio@artemio.net> <20030611225401.GE2712@werewolf.able.es> In-Reply-To: <20030611225401.GE2712@werewolf.able.es> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1001 Lines: 23 J.A. Magallon wrote: > In short, for FP intensive tasks, hyperthreading is a big lie... > You can't run 2 computations in parallel. Yes and no; the benefit of HT depends on the application in question. I've seen everything from a 5% LOSS in performance to a 30% INCREASE in performance, for intensive floating-point code. This is with programs parallelized with OpenMP and Intel's C and Fortran compilers. I'm still analyzing the exact nature of the benefits, but they *do* exist. While I much prefer multiple physical CPUs to "virtual" CPUs, HT *does* provide performance improvements for certain applications. To call HT a "big lie" is both provacative and inaccurate. -- Scott Robert Ladd Coyote Gulch Productions (http://www.coyotegulch.com) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/