> On Wed, 5 Aug 2009 12:19:23 +0200 Roland Smith <rsm...@xs4all.nl> wrote: > >On Wed, Aug 05, 2009 at 10:54:07AM +0100, David Southwell wrote: > >> I have found > >> http://docs.freebsd.org/info/gcc/gcc.info.Optimize_Options.html. > >> > >> I am about to build a new kernel am starting to dig a bit deeper into > >> things I have, until now, taken for granted. > >> > >> The above link is very informative in technical terms about how to > >> control optimization but I find it difficult to interpret the info in a > >> way that tells me what might work best on my own system (Intel quad > >> Core) with 8G of ram. > > > >The build system takes care of that, once you have set the correct > >CPUTYPE in /etc/make.conf. For a quad-core, set CPUTYPE=nocona. See > >make.conf(5), /usr/src/share/mk/bsd.cpu.mk and > >/usr/src/sys/conf/kern.pre.mk. > > As I read the man page for [g]cc, though, setting -march=nocona (which > is where the CPUTYPE information ends up in the cc commands) tells the > compiler which base instruction set to use and which model of instruction > scheduling to use, but to get the rest of the model-dependent features > used, he would still need to add "-mmmx -msse -msse2 -msse3" at a minimum > for most other compilations, though these would not be advisable for kernel > compilations. I don't recall whether SSE4 instructions are in the Nocona/ > Merom/Kentfield chips or first appear in the Core i7 series. I don't think > the compiler versions available under FreeBSD support the SSE4 > instructions, though, so SSE4 doesn't matter anyway. > > >Additionally, compiler settings for building the kernel can be set with > >COPTFLAGS in /etc/make.conf. Using anything other than -O or -O2 is > >not guaranteed to work. If you don't know what you are doing, do not use > >COPTFLAGS and stick with the defaults that the build system generates. > > Right. -O3 might royally screw a kernel in particular. :-) > > > Scott Bennett, Comm. ASMELG, CFIAG Thanks for add more useful info however would you mind elaborating a little more because I do not understand the implications.
should I have: CPUTYPE=nocona in make.conf? Do I need anything else in make.conf? So far my draft make.conf has these entries: CPUTYPE=nocona CFLAGS= -O2 -fno-strict-aliasing -pipe FORCE_MAKE_JOBS= true Incidentally I am also puzzled because it appears necessary to use amd64 GENERIC as my starting point when the cpu is actually Intel Quad Core!! I presume this means that in drafting a kernconf I need to refer to; dns1# pwd /usr/src/sys/amd64/conf dns1# ls -l total 44 -rw-r--r-- 1 root wheel 13 Jun 20 2005 .cvsignore -rw-r--r-- 1 root wheel 482 Apr 15 04:14 DEFAULTS -rw-r--r-- 1 root wheel 11968 Apr 15 04:14 GENERIC -rw-r--r-- 1 root wheel 818 Apr 15 04:14 GENERIC.hints -rw-r--r-- 1 root wheel 1036 Apr 15 04:14 MAC -rw-r--r-- 1 root wheel 132 Apr 15 04:14 Makefile -rw-r--r-- 1 root wheel 20721 Apr 15 04:14 NOTES It would be great if some logical consistency could be introduced into naming conventions!!! It would really help those of us who know little and make it a trifle easier to climb the greasy pole of knowledge <chuckles> _______________________________________________ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org"
