Date: Wed, 5 Aug 2009 14:49:06 +0100 From: David Southwell <david@vizion2000.net> To: Roland Smith <rsmith@xs4all.nl> Cc: Scott Bennett <bennett@cs.niu.edu>, freebsd-questions@freebsd.org Subject: Re: Learning about Control of Optimization -- for dummies please Message-ID: <200908051449.06688.david@vizion2000.net> In-Reply-To: <20090805133648.GB30790@slackbox.xs4all.nl> References: <200908051238.n75CcKC1006683@mp.cs.niu.edu> <200908051402.06130.david@vizion2000.net> <20090805133648.GB30790@slackbox.xs4all.nl>
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> On Wed, Aug 05, 2009 at 02:02:05PM +0100, David Southwell wrote: > > > >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? > > Yes. > > > Do I need anything else in make.conf? > > If you are building a custom kernel, you can set the name of the kernel > config there. E.g.: > > KERNCONF=FOO > > You should then put your kernel config in /usr/src/sys/amd64/conf/FOO. > > > So far my draft make.conf has these entries: > > > > CPUTYPE=nocona > > OK. > > > CFLAGS= -O2 -fno-strict-aliasing -pipe > > CFLAGS are used for building userland programs. COPTFLAGS are used for > building the kernel. I think that the values you've listed here are already > the default, so they are superfluous really. > > > FORCE_MAKE_JOBS= true > > This is only for ports. > > > 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!! > > This is a FAQ. AMD originated the 64-bit extensions to the x86 > architecture while intel was chasing the itanium pipedream. This > extended architecture became known as x86_64 or amd64. After itanium > became a dud, intel started making amd64 compatible chips as well, > because the AMD chips had been hugely successfull. > > > 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 > > Some options were moved to a DEFAULT file that is automatically included > in every kernel, so that people can't forget them. Formetting one of > those can result in an unusable kernel. > > > -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 > > NOTES contains extra options that aren't in the GENERIC kernel. > > > 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> > > Just look at the beginning of each file. You'll find a description of > that files purpose. > > You should base you kernel configuration on the GENERIC kernel. The > first thing you need to do is change the "ident" line to match the > filename. A kernel config FOO should include "ident FOO". Then remove > devices and options that you don't need. If you don't know what a device > or option is, leave it in. For devices, there is usually a manual > page. E.g. if you see 'device em', you can get information about it with > 'man em'. > > Look at the dmesg(8) output to see which devices you actually have. > > Roland Roland Thank you I will be digging around and try and make good use of yr advice David
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