From owner-freebsd-stable@FreeBSD.ORG Sat Nov 11 01:31:00 2006 Return-Path: X-Original-To: freebsd-stable@freebsd.org Delivered-To: freebsd-stable@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 19C6916A415 for ; Sat, 11 Nov 2006 01:31:00 +0000 (UTC) (envelope-from elessar@bsdforen.de) Received: from mail.bsdforen.de (bsdforen.de [212.204.60.79]) by mx1.FreeBSD.org (Postfix) with ESMTP id 9DE1E43D4C for ; Sat, 11 Nov 2006 01:30:59 +0000 (GMT) (envelope-from elessar@bsdforen.de) Received: from localhost (mail [127.0.0.12]) by mail.bsdforen.de (Postfix) with ESMTP id 7FB5F4241CA; Sat, 11 Nov 2006 02:30:58 +0100 (CET) X-Virus-Scanned: amavisd-new at bsdforen.de Received: from mail.bsdforen.de ([127.0.0.12]) by localhost (mail.bsdforen.de [127.0.0.12]) (amavisd-new, port 10024) with ESMTP id cIfceNZz+faq; Sat, 11 Nov 2006 02:30:58 +0100 (CET) Received: from loki.starkstrom.lan (p549CE2FA.dip.t-dialin.net [84.156.226.250]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.bsdforen.de (Postfix) with ESMTP id 5ABB24241C0; Sat, 11 Nov 2006 02:30:55 +0100 (CET) Date: Sat, 11 Nov 2006 02:30:51 +0100 From: Joerg Pernfuss To: freebsd-stable@freebsd.org Message-ID: <20061111023051.38dbaa37@loki.starkstrom.lan> In-Reply-To: <200611111019.43944.doconnor@gsoft.com.au> References: <4554D43E.5010700@highperformance.net> <20061110222434.GA76724@icarus.home.lan> <200611111019.43944.doconnor@gsoft.com.au> X-Mailer: Sylpheed-Claws 2.5.2 (GTK+ 2.8.20; i386-portbld-freebsd6.1) Mime-Version: 1.0 Content-Type: multipart/signed; boundary=Sig_04Vhn.2bNPaHYz9VOtlqoSB; protocol="application/pgp-signature"; micalg=PGP-SHA1 Cc: "Jason C. Wells" , Jeremy Chadwick Subject: Re: Compiler Options X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 11 Nov 2006 01:31:00 -0000 --Sig_04Vhn.2bNPaHYz9VOtlqoSB Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Sat, 11 Nov 2006 10:19:42 +1030 "Daniel O'Connor" wrote: > On Saturday 11 November 2006 08:54, Jeremy Chadwick wrote: > > The kernel itself _will not_ use any SSE or MMX operations when > > built. This is because these optimisations are known to break the > > FreeBSD kernel. This applies to all i386 architectures, and > > probably 64-bit architectures too (not sure). >=20 > I think this is mainly because the kernel has no FPU context so you > can't actually use any FPU operation (including SSE & MMX) without > potentially trashing userland data. If I remember correctly, this was the reason why some improvements from DragonFlyBSD were not ported to FreeBSD (or were ported but not committed). There was no conclusive evidence that the speed improvement for some operations would result in a net gain, due to register saving/restoring overhead during context switches. > (I could be wrong but the above is what I remember reading on various > lists over the years :) I think you remember right. Or I remember wrong too :) Joerg --=20 | /"\ ASCII ribbon | GnuPG Key ID | e86d b753 3deb e749 6c3a | | \ / campaign against | 0xbbcaad24 | 5706 1f7d 6cfd bbca ad24 | | X HTML in email | .the next sentence is true. | | / \ and news | .the previous sentence was a lie. | --Sig_04Vhn.2bNPaHYz9VOtlqoSB Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2.2 (FreeBSD) iD8DBQFFVSfLH31s/bvKrSQRAqsuAJ9HgCHBNXadTC+qOC/Lhl7kUX58YwCfQu6i cTDVkYpk+w7blSEskTa6wXM= =t49V -----END PGP SIGNATURE----- --Sig_04Vhn.2bNPaHYz9VOtlqoSB--