Jean Francois Martinez wrote: > On Tue, 2002-11-05 at 17:38, Thomas Dodd wrote: > www.linuxgazette.com february 1999 I'll read it later. >>What compiler? gcc-3 is supposed to have better optimization. >>Perhaps the numbers would be different now? > It was gcc 2.7. But while gcc has changed so have the distributions: at > that time distros shipped only one kernel since gcc 2.7 performed very > little processor-specific optimizations and there was very little code > in the kernel directly related to processor type (the memcpy code, page > protection and selective invalidation of TLB entries). Today this is no > longer valid but RedHat ships processor-specific kernels Whuch started this. They no longer ship an i386 kernel. Anything that won't boot/run an i586 kernel is not installable now. > You _could_ gain a benefit if you are still using a Pentium MMX or a K6: > both will get a Pentium kernel and code optimized for Pentium will suck > on anything else MMX included. For the K6 I recommend hacking the > compiler flags and using -mcpu=i686 (NOT -march=i686) instead of > -march=k6 . Gcc generates some slow code when told to optimize for the > K6 specially on bit operations who are frequently used in kernel. Is that still the case with gcc-3 and the 2.4 kernels? Is that documented somwhere? I've been running custom built kernel, and selecting K6 in the config since it was added to the kernel. Why would code "optimized" for the K6 run slow on the K6? Why even have the -march=k6 code path if it's slow? > But MMX and K6 are now quite rare. More rare that the pre MMX Pentium? I have 4 machines that run linux. A 486, a K6, a K6-III, and a Athlon (SlotA T-bird). I have some old 68000 stuff too, but no linux on them. I would expect more K6(including 2 and 3), MMX Pentiums, Cyrix, and pre i586 CPUs (in that order) still running, than nonMMX Pentiums. The fastest kernel for those would be i386 not i586, due to the weird optimization for the Pentium. So the best averall, for most pre i686 system would be i386 right? How much slower is an i586 kernel on a MMX Pentium than the i386 version? -Thomas -- Psyche-list mailing list Psyche-list@redhat.com https://listman.redhat.com/mailman/listinfo/psyche-list
