From owner-freebsd-questions@FreeBSD.ORG Tue Nov 15 00:21:33 2005 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 819C416A447 for ; Tue, 15 Nov 2005 00:21:33 +0000 (GMT) (envelope-from kris@obsecurity.org) Received: from elvis.mu.org (elvis.mu.org [192.203.228.196]) by mx1.FreeBSD.org (Postfix) with ESMTP id 3B33E43D45 for ; Tue, 15 Nov 2005 00:21:33 +0000 (GMT) (envelope-from kris@obsecurity.org) Received: from obsecurity.dyndns.org (elvis.mu.org [192.203.228.196]) by elvis.mu.org (Postfix) with ESMTP id 1B4FA1A3C2D; Mon, 14 Nov 2005 16:21:33 -0800 (PST) Received: by obsecurity.dyndns.org (Postfix, from userid 1000) id 58E7E512D3; Mon, 14 Nov 2005 19:21:32 -0500 (EST) Date: Mon, 14 Nov 2005 19:21:32 -0500 From: Kris Kennaway To: Chris Message-ID: <20051115002132.GB67157@xor.obsecurity.org> References: <20051114102308.7515.GERARD@seibercom.net> <20051114202300.GB98749@xor.obsecurity.org> <43792010.9010802@childeric.freeserve.co.uk> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="p4qYPpj5QlsIQJ0K" Content-Disposition: inline In-Reply-To: <43792010.9010802@childeric.freeserve.co.uk> User-Agent: Mutt/1.4.2.1i Cc: freebsd-questions@freebsd.org Subject: Re: Makefile and Kernel Optimizations in 6.0 X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 15 Nov 2005 00:21:33 -0000 --p4qYPpj5QlsIQJ0K Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Nov 14, 2005 at 11:38:56PM +0000, Chris wrote: > Kris Kennaway wrote: > >P.S. -funroll-loops and -ffast-math are commonly used by people who > >don't understand what they mean but like the thrill it gives them to > >compile their application with secret optimizations (e.g. the word > >"fast" makes them feel excited). However, the former is often not > >actually an optimization (which is why it's not on by default), and > >the latter can cause incorrect computations (but I think it's > >completely irrelevant in the kernel which does not do FP math). >=20 > Just out of curiosity, what would people who know what they are doing=20 > use them for? -funroll-loops sounds like an amusement park :P They would carefully test to see whether it helped their specific CPU-intensive application, and only use it if so. Kris --p4qYPpj5QlsIQJ0K Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (FreeBSD) iD8DBQFDeSoLWry0BWjoQKURAkI7AKDuQoCEJyDL7C1ivx5PspPygCkBawCeLUAf tbBXdX3g1mzyJ4QvlHjZUI0= =IGxl -----END PGP SIGNATURE----- --p4qYPpj5QlsIQJ0K--