Messages in this thread |  | | | Date | Sat, 13 Sep 2003 23:52:37 +0200 | | From | Adrian Bunk <> | | Subject | Re: RFC: [2.6 patch] better i386 CPU selection |
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On Sat, Sep 13, 2003 at 07:35:29PM +0100, Dave Jones wrote: > On Sat, Sep 13, 2003 at 08:22:12PM +0200, Adrian Bunk wrote: > > > What does a user think on which machines a kernel will run after he > > enabled the following options? > > - "Athlon/Duron/K7" > > - "Generic x86 support" > > Currently, as you can only choose one of them, it should be obvious. > With your 'you can choose n number of options' patch, it becomes > confusing why there is a generic option at all.
No, currently you first choose the CPU. This CPU selection selects most settings like the CPU features (e.g. enables X86_F00F_BUG) and the gcc optimization flags.
The "Generic x86 support" question is asked later.
My patch removes the generic option since it's no longer needed.
>... > > > Incidentally, looking closer you broke this option. > > > > > > +ifdef CONFIG_CPU_VIAC3_2 > > > + cpuflags-y := $(call check_gcc,-march=c3,-march=i686) > > > +endif > > > > > > Its C3_2 becauase it needs -march=c3-2 to use SSE instead of 3dnow > > > prefetches. One thing that just occured to me, it may be possible > > >... > > > > Which gcc does support -march=c3-2 ? gcc 3.3.1 doesn't support it. > > the 3.3.2 and 3.4 branches have it.
Ah I didn't know that. The 20030831 snapshot of the 3.3 branch in Debian unstable was the latest gcc I checked.
> > > And "You can select 486/586/686 too" is not an answer. These kernels > > > need to be small, and errata workarounds should NEVER be compiled out > > > for exactly this reason. > > >... > > Why is a kernel compiled with support for all CPUs necessarily much > > bigger than a current M386 kernel? > > Adding in stuff like cpu specific memory copy routines for example. > There have been several cases where vendors haven't been able to squeeze a > boot kernel onto a CD by 40 or so bytes in the past, leading to a last > minute scavenge to try and reclaim that space. Every little helps. > > > OTOH, why waste space on a 486 for 3DNow! support? > > I'm arguing for errata workarounds, not extended support.
I'll send the cpu selection patch with the arch/i386/kernel/cpu/ and arch/i386/kernel/cpu/mtrr/ stuff as separate patches.
> Dave
cu Adrian
--
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