Date: Sat, 11 Nov 2006 10:19:42 +1030 From: "Daniel O'Connor" <doconnor@gsoft.com.au> To: freebsd-stable@freebsd.org Cc: "Jason C. Wells" <jcw@highperformance.net>, Jeremy Chadwick <freebsd@jdc.parodius.com> Subject: Re: Compiler Options Message-ID: <200611111019.43944.doconnor@gsoft.com.au> In-Reply-To: <20061110222434.GA76724@icarus.home.lan> References: <4554D43E.5010700@highperformance.net> <20061110222434.GA76724@icarus.home.lan>
next in thread | previous in thread | raw e-mail | index | archive | help
--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--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200611111019.43944.doconnor>