Oops. Gcc 3.2 is able to optimize for P4. On Wed, 2003-06-11 at 00:07, Jean Francois Martinez wrote: > On Tue, 2003-06-10 at 08:59, Christos E. Chrisostomidis wrote: > > Dear all, > > > > Most of the RPM packages shipped with RH9 (and older), come for a i386 > > target. > > > > I am having a pentium 4 box and I am currently using rpmbiuld > > --rebuild --target i686 to rebuild > > the SRPMs in order to optimize performance. > > > > I am trying to optimize packages such as sendmail, samba, squid etc. > > First of all before you go into a frenzy of package rebuilding how > about MEASURING the performance of a CPU intensive benchmark both > using RedHat default parms (who BTW target the i686 for optim purposes) > and what you get when compiler is using the same parms than an rpm > built with --target i686? > > And once you have done that what about EVALUATING if it is worth the > trouble? > > In case you still go for it there are a couple of caveats: > 1) Gcc 3.2 does not optimize for the Pentium 4. It only knows about the > i686 family (PPro to PIII) who is very different for optimization > purposes. In fact you could try to play with other -mcpu= parms since > it could happen than another CPU has a timetable closer to the PIV than > the PIII family. It _could_ happen that your P4 were faster with > say, -mcpu=i386 or -mcpu=athlon than with -mcpu=i686. > > 2) Whenever the program enters glibc or kernel you will be gaining > nothing since RedHat already ships optimized RPMs for these. > > 3) RedHat does not invoke gcc with parms for MMX/SSE instructions since > the i686 packages are supposed to run on PPro. I expect them giving a > real boost on some programs. However I also expect you run into some > interesting bugs since this is relatively uncharted territory. But > since the only way to debug GCC's MMX/SSE code generation is for people > using it I strongly encorage you to boldly go where no geek has > ventured before. :-) > > > > > > I am wondering if I need to specify any gcc/g++ compiler optimization > > flags, perhaps in the form of an rpmrc file. > > > > If this is the case, does anybody knows a good reference to look at so > > I can find the appropriate optflags > > to use ? > > > > > > Best Regards > > Christos > > > > > -- > Jean Francois Martinez <jfm512@xxxxxxx> -- Jean Francois Martinez <jfm512@xxxxxxx>
