Messages in this thread | | | Date | Sat, 13 Sep 2003 19:35:29 +0100 | From | Dave Jones <> | Subject | Re: RFC: [2.6 patch] better i386 CPU selection |
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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.
> > > If you read the description of X86_GENERIC it implicitely says a kernel > > > for a 386 isn't generic. > > Apart from using incorrect cache line alignments on P4, an i386 kernel > > is no more, no less generic than one compiled with X86_GENERIC > plus X86_INTEL_USERCOPY
Sure, but that still doesn't prevent it being used on any system as a generic kernel.
> > 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.
> > 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.
Dave
-- Dave Jones http://www.codemonkey.org.uk - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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