From owner-freebsd-hackers@FreeBSD.ORG Wed Mar 30 03:46:49 2005 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 6289D16A4CE for ; Wed, 30 Mar 2005 03:46:49 +0000 (GMT) Received: from ms-smtp-03-eri0.southeast.rr.com (ms-smtp-03-lbl.southeast.rr.com [24.25.9.102]) by mx1.FreeBSD.org (Postfix) with ESMTP id AEE0F43D48 for ; Wed, 30 Mar 2005 03:46:48 +0000 (GMT) (envelope-from jason@ec.rr.com) Received: from [192.168.1.100] (cpe-065-184-201-054.ec.rr.com [65.184.201.54]) j2U3kjY4024111; Tue, 29 Mar 2005 22:46:45 -0500 (EST) Message-ID: <424A23A8.5040109@ec.rr.com> Date: Tue, 29 Mar 2005 22:57:28 -0500 From: jason henson User-Agent: Mozilla Thunderbird 1.0 (X11/20050321) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Peter Jeremy References: <423C15C5.6040902@fsn.hu> <20050327133059.3d68a78c@Magellan.Leidinger.net> <20050327134044.GM78512@silverwraith.com> <20050327162839.2fafa6aa@Magellan.Leidinger.net> <5bbfe7d405032823144fc1af7b@mail.gmail.com> <5bbfe7d405032823232103d537@mail.gmail.com> <20050329111107.GD69824@cirb503493.alcatel.com.au> In-Reply-To: <20050329111107.GD69824@cirb503493.alcatel.com.au> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: Symantec AntiVirus Scan Engine cc: David Leimbach cc: hackers@freebsd.org Subject: Re: Fwd: 5-STABLE kernel build with icc broken X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 30 Mar 2005 03:46:49 -0000 Peter Jeremy wrote: >On Mon, 2005-Mar-28 23:23:19 -0800, David Leimbach wrote: > > >>meant to send this to the list too... sorry >> >> >>>Are you implying DragonFly uses FPU/SIMD? For that matter does any kernel? >>> >>> >>I believe it does use SIMD for some of it's fast memcopy stuff for >>it's messaging system >>actually. I remember Matt saying he was working on it. >> >>http://leaf.dragonflybsd.org/mailarchive/kernel/2004-04/msg00262.html >> >> > >That's almost a year ago and specifically for the amd64. Does anyone >know what the results were? > > > >>If you can manage the alignment issues it can be a huge win. >> >> > >For message passing within the kernel, you should be able to mandate >alignment as part of the API. > >I see the bigger issue being the need to save/restore the SIMD >engine's state during a system call. Currently, this is only saved on >if a different process wants to use the SIMD engine. For MMX, the >SIMD state is the FPU state - which is non-trivial. The little >reading I've done suggests that SSE and SSE2 are even larger. > >Saving the SIMD state would be more expensive that using integer >registers for small (and probably medium-sized) copies. > > > Later in that thread they discuss skipping the restore state to make things faster. The minimum buffer size they say this will be good for is between 2-4k. Does this make sense, or am I showing my ignorance? http://leaf.dragonflybsd.org/mailarchive/kernel/2004-04/msg00264.html