From owner-freebsd-amd64@FreeBSD.ORG Thu Jul 28 16:36:02 2005 Return-Path: X-Original-To: freebsd-amd64@freebsd.org Delivered-To: freebsd-amd64@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id EB44116A420 for ; Thu, 28 Jul 2005 16:36:02 +0000 (GMT) (envelope-from sgk@troutmask.apl.washington.edu) Received: from troutmask.apl.washington.edu (troutmask.apl.washington.edu [128.208.78.105]) by mx1.FreeBSD.org (Postfix) with ESMTP id 5631A43D4C for ; Thu, 28 Jul 2005 16:36:02 +0000 (GMT) (envelope-from sgk@troutmask.apl.washington.edu) Received: from troutmask.apl.washington.edu (localhost [127.0.0.1]) by troutmask.apl.washington.edu (8.13.4/8.13.4) with ESMTP id j6SGa2cN064330; Thu, 28 Jul 2005 09:36:02 -0700 (PDT) (envelope-from sgk@troutmask.apl.washington.edu) Received: (from sgk@localhost) by troutmask.apl.washington.edu (8.13.4/8.13.1/Submit) id j6SGa2Rn064329; Thu, 28 Jul 2005 09:36:02 -0700 (PDT) (envelope-from sgk) Date: Thu, 28 Jul 2005 09:36:02 -0700 From: Steve Kargl To: ray@redshift.com Message-ID: <20050728163602.GC64153@troutmask.apl.washington.edu> References: <3.0.1.32.20050728080526.00aa4098@pop.redshift.com> <86mzo7yvpe.fsf@xps.des.no> <3.0.1.32.20050728013152.00a4d188@pop.redshift.com> <86mzo7yvpe.fsf@xps.des.no> <3.0.1.32.20050728080526.00aa4098@pop.redshift.com> <3.0.1.32.20050728092338.01207628@pop.redshift.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3.0.1.32.20050728092338.01207628@pop.redshift.com> User-Agent: Mutt/1.4.2.1i Cc: freebsd-amd64@freebsd.org Subject: Re: Benchmarks: AMD64 vs i386 on Dual 246 Opteron X-BeenThere: freebsd-amd64@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Porting FreeBSD to the AMD64 platform List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 28 Jul 2005 16:36:03 -0000 On Thu, Jul 28, 2005 at 09:23:38AM -0700, ray@redshift.com wrote: > | > | Drop 8 GB of memory into the box and see how the 32-bit > | FreeBSD performs in comparison to the 64-bit FreeBSD > | when your process consumes greater than 4GB of memory. > > True, once you go over the 4GB limit it's a different ball of wax. > However, until that time, it would be nice to get to the bottom of > why 64 bit code is running half the speed of 32 bit code on the exact > same machine - don't you think? Well, I have 12 GB of memory and run numerical intensive codes that easily can grab 4+ GB, so I've never explored i386 FreeBSD on an amd64 system. As mentioned elsewhere, I would look for optimizations within the software packages that target i386. Additionally, the instruction schedulers in gcc/gas have had many more years of development in comparison to the amd64 schedulers. An interesting test would be to build math/atlas on 32-bit and 64-bit FreeBSD and then run some linpack benchmarks. -- Steve