Messages in this thread |  | | | Subject | Re: [PATCH] 2.6 workaround for Athlon/Opteron prefetch errata | | From | Martin Schlemmer <> | | Date | Fri, 12 Sep 2003 21:05:06 +0200 |
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On Fri, 2003-09-12 at 20:28, Andi Kleen wrote: > On Fri, 12 Sep 2003 20:22:16 +0200 > Adrian Bunk <bunk@fs.tum.de> wrote: > > > > > > But even CONFIG_X86_GENERIC doesn't do what you expect. A kernel > > compiled for Athlon wouldn't run on a Pentium 4 even with > > CONFIG_X86_GENERIC. > > It does. Just try it. > > > > > Quoting arch/i386/Kconfig in -test5: > > > > <-- snip --> > > > > config X86_USE_3DNOW > > bool > > depends on MCYRIXIII || MK7 > > default y > > That's obsolete and could be removed. All 3dnow! code is dynamically patched depending on the CPUID. >
Ok, so how many instructions was added by this ? Or is it just in the init code ? What else just add 'just another one or two instructions' to common paths because of this?
Which ever way, the point I and some of the others (besides the additional one from the embedded guys) want to make, is if I select the CPU to be Pentium4, it means I want a kernel that is optimised for my P4, without extra crap that I do not need. Sure, its an extra instruction here, two there, etc - but when will it be too much ? Is this not maybe the fabled 'slight slowdown' that so many people complain about from round the 2.5.[67]'s ?
Ok, so maybe my opinion about X86_GENERIC is not as intended, but then IMHO, it should be 'fixed'. I could not care less if my kernel only boot just on my box, never mind on another P4 - I just want the most optimised on possible. Sure, some guys want a more generic kernel - get X86_GENERIC to work for them. Same for distro's.
I have long wondered if everything in arch/i386/kernel/cpu/ is really linked in (meaning with no #ifdef as it now looks to be at a quick peek), or if it was just easier to link them all, but have non generic stuff (amd/cyrix/whatever specific code) filtered by ifdef's.
This is just me, but why then don't we then just drop the specific arch selection, and just have generics instead of pulling a sock over the user's eyes ?
Thanks,
-- Martin Schlemmer
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