On Sat, 2017-03-04 at 15:49 -0500, Pedro Giffuni wrote: > > > > Il giorno 04 mar 2017, alle ore 14:43, John Baldwin <j...@freebsd.or > > g> ha scritto: > > > > On Saturday, March 04, 2017 10:52:46 AM Pedro Giffuni wrote: > > > > > > > > > On 03/04/17 10:32, Slawa Olhovchenkov wrote: > > > > > > > > On Sat, Mar 04, 2017 at 03:04:17PM +0000, Pedro F. Giffuni > > > > wrote: > > > > > > > > > > > > > > Author: pfg > > > > > Date: Sat Mar 4 15:04:17 2017 > > > > > New Revision: 314669 > > > > > URL: https://svnweb.freebsd.org/changeset/base/314669 > > > > > > > > > > Log: > > > > > Drop i486 from the default i386 GENERIC kernel > > > > > configuration. > > > > > > > > > > 80486 production was stopped by Intel on September 2007. > > > > > Dropping the 486 > > > > > configuration option from the GENERIC kernel improves > > > > > performance > > > > > slightly. > > > > > > > > > > Removing I486_CPU is consistent at this time: we don't > > > > > support any > > > > > processor without a FPU and the PC-98 arch, which frequently > > > > > involved i486 > > > > > CPUs, is also gone so we don't test such platforms anymore. > > > > What is realy mean? > > > This means we don't do work-arounds that would be required for > > > raw 486. > > > Instead we will use the 586 instructions by default. > > This doesn't change that. The kernel already has runtime tests in > > place > > for new things on 486 and later via cpuid. > > > Hmm ..then I am wondering if I effectively changed anything? > > > > > > > > > > > > > > Some Via CPU is like i486 (by instruction set). > > > > > > > > CPU: VIA Ezra (800.04-MHz 686-class CPU) > > > > Origin="CentaurHauls" Id=0x678 Family=0x6 Model=0x7 Steppi > > > > ng=8 > > > > Features=0x803035<FPU,DE,TSC,MSR,MTRR,PGE,MMX> > > > > AMD Features=0x80000000<3DNow!> > > > > > > > 486 never had MMX extensions. > > > This is a 686, performance should improve ~4%. > > How did you measure the improvement? Keeping I486_CPU doesn't > > really > > do anything except remove a some #ifdef'd conditionals in > > identcpu.c > > and initcpu.c. It doesn't affect whether we use the TSC, MMX, > > etc. Those > > are all runtime checks based the CPU feature flags from cpuid. > > > The number came out from an old posting involving buildworld times, > which I can’t find now :(. > Things seem to have changed a lot: it was surely using GCC back then, > I don’t believe clang does much distinction about 486 at all. > > BTW, does it make sense to keep i586 in the configuration still? Both > i486 and i586 were once removed but later re-instated in r205336. > > Pedro.
i586 hardware which is not also i686 is still alive and well, but I think at this point it's mostly used in specialized applications. I have no problem with removing i586 from GENERIC, but please don't remove underlying support for setting it in custom kernel configs. -- Ian _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
