From owner-freebsd-stable@FreeBSD.ORG Fri Nov 10 23:49:48 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 AB83916A412 for ; Fri, 10 Nov 2006 23:49:48 +0000 (UTC) (envelope-from doconnor@gsoft.com.au) Received: from cain.gsoft.com.au (cain.gsoft.com.au [203.31.81.10]) by mx1.FreeBSD.org (Postfix) with ESMTP id DCEAE43D53 for ; Fri, 10 Nov 2006 23:49:47 +0000 (GMT) (envelope-from doconnor@gsoft.com.au) Received: from inchoate.gsoft.com.au (ppp218-17.lns1.adl2.internode.on.net [203.122.218.17]) (authenticated bits=0) by cain.gsoft.com.au (8.13.5/8.13.4) with ESMTP id kAANniVD007798 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Sat, 11 Nov 2006 10:19:45 +1030 (CST) (envelope-from doconnor@gsoft.com.au) From: "Daniel O'Connor" To: freebsd-stable@freebsd.org Date: Sat, 11 Nov 2006 10:19:42 +1030 User-Agent: KMail/1.9.4 References: <4554D43E.5010700@highperformance.net> <20061110222434.GA76724@icarus.home.lan> In-Reply-To: <20061110222434.GA76724@icarus.home.lan> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart11079608.24LJcAflY1"; protocol="application/pgp-signature"; micalg=pgp-sha1 Content-Transfer-Encoding: 7bit Message-Id: <200611111019.43944.doconnor@gsoft.com.au> X-Spam-Score: 0 () X-Scanned-By: MIMEDefang 2.57 on 203.31.81.10 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: Fri, 10 Nov 2006 23:49:48 -0000 --nextPart11079608.24LJcAflY1 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline 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). I think this is mainly because the kernel has no FPU context so you can't=20 actually use any FPU operation (including SSE & MMX) without potentially=20 trashing userland data. Also, the cost of saving/restoring the context is quite high so potential=20 benefits are largely negated. (I could be wrong but the above is what I remember reading on various lists= =20 over the years :) =2D-=20 Daniel O'Connor software and network engineer for Genesis Software - http://www.gsoft.com.au "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C --nextPart11079608.24LJcAflY1 Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.5 (FreeBSD) iD8DBQBFVRAX5ZPcIHs/zowRArNlAJwOOwTNzwH95rp04ssSQCB/H4bT5QCfaWC3 RahEq7Lo9L6ExkTQL/mWFCA= =MBUs -----END PGP SIGNATURE----- --nextPart11079608.24LJcAflY1--