Man, my typing sucked in that last one... Mike A. Harris wrote: > On Mon, 21 Oct 2002, Thomas Dodd wrote: >>Except a i586 kerenl is horrribly slow on a K6. > I've never done an in depth comparison, but I wouldn't consider > it to be all that bad. The K6 should reorder things internally I > would presume anyway to be more optimal. Have you done any Not sure there. The instruction mix from the compiler should be different, causing problems for the schedulers. > benchmarking? I used to use home brew K6 kernels, but then > switched to stock kernels not long after starting at Red Hat. QA > testing became more important to me. ;o) No idea what to bench with. The whole problkem with benckmarking is timing the right things and figuring out what it means :) >>So owners of a true Pentium would probably benifit from >>a -mcpu=i586 version of glibc. Since it would give a more optimum instruction mix. >>My understanding is that the i586 scheduler (compiler) creates >>code that only runs well on an actuall *ntel Pentium. Not a K5, >>K6, or Cyrix. Not a i686 (PPRo, PII, or PIII), not a Pentium w/ >>MMX. > > > That is a reasonable assumption. Note however that newer CPU's > internally reorder instruction execution to be more optimal at > runtime. When the PII and K6-2 came out, I remember the optimization guide saying that the new CPUs ran i386 optimized code faster than pentium optimized code, and to not use the pentium guidelines anymore. > There is no question at all, that providing a kernel customized > for every single CPU brand/model would be most optimal for that > particular CPU brand/model. That isn't however remotely Didn't mean that ;) But if most pre i686 CPUS (pre PPro/PII/Athlon) run the i386 code mix faster than the pentium mix, why not supply the i386 mix. I woul thing there are more 486s, P/MMX, K5, K6, and Cyrix CPUs still in use than Pentiums (pre MMX). > An athlon glibc would be nice to test. Not sure if it would > provide noticeable difference or not as I'm not sure if gcc > takes advantage of anything new in the athlon instruction set or > not. Athlon optimized string operations would be nice, but I > don't think gcc takes advantage of anything that useful on athlon > yet. It'd be very cool though to have if one of the compiler > guys could provide info about gcc's athlon optimizations, and if > someone would implement useful tidbits if it hasn't been done > already. > > If anyone experiments with a glibc rebuild, be sure to do some > before and after benchmarking with useful tests and post back to > the list. > > I'd give it a crack myself, but I don't have an Athlon handy to > muck around with. ;o/ I'd do it, but I havent a clue how to build glibc that way, or how to test the results. -Thomas -- Psyche-list mailing list Psyche-list@redhat.com https://listman.redhat.com/mailman/listinfo/psyche-list
