Date: Mon, 11 Dec 2000 09:29:14 -0600 From: "Thomas T. Veldhouse" <veldy@veldy.net> To: "Mark Powell" <M.S.Powell@salford.ac.uk> Cc: <freebsd-stable@freebsd.org> Subject: Re: Different gcc optimisations cause IP packet CRC problems Message-ID: <00af01c06387$1ecb5230$9c29680a@tgt.com> References: <Pine.BSF.4.21.0012111513500.36265-100000@plato.salford.ac.uk>
next in thread | previous in thread | raw e-mail | index | archive | help
I generally don't compile the kernel with any optimizations except "-O -pipe". I never have a problem - and I don't have any performance differences that have been noticable. Tom Veldhouse veldy@veldy.net ----- Original Message ----- From: "Mark Powell" <M.S.Powell@salford.ac.uk> To: <freebsd-stable@freebsd.org> Sent: Monday, December 11, 2000 9:24 AM Subject: Different gcc optimisations cause IP packet CRC problems > Hi, > On a PIII 600E, compiling a week old 4.2S kernel with the following > options: > > -O2 -fomit-frame-pointer -mpentium -march=pentium -pipe > > Cause the kernel to produce TCP CRC errors when talking to certain IP > addresses. It generally seemed to get the 2nd octet of the CRC out by one > i.e. 0xb9f7 became 0xbaf7 etc. > I originally did this, because I was using this fastish machine to > remake world for another P166 machine. I forgot to change it back and > accidentally recompiled it's own kernel with the above settings. > This problem was fixed by simply changing the gcc optimisation to the > correct CPU type: > > -O2 -fomit-frame-pointer -mpentiumpro -march=pentiumpro -pipe > > However, shouldn't the PIII be backwards compatible with any Pentium code? > Or are there some incorrect assumptions made in the CRC generation code? > Cheers. > > BTW Where in the source is the CRC generated? > > Mark Powell - UNIX System Administrator - The University of Salford > Academic Information Services, Clifford Whitworth Building, > Salford University, Manchester, M5 4WT, UK. > Tel: +44 161 295 5936 Fax: +44 161 295 5888 www.pgp.com for PGP key > > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-stable" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?00af01c06387$1ecb5230$9c29680a>