Messages in this thread | | | Date | Tue, 22 Jul 1997 09:55:03 -0600 (MDT) | From | Teunis Peters <> | Subject | Re: Kernel cpu selection + other platforms? |
| |
On Tue, 22 Jul 1997, Mike Jagdis wrote:
> On Mon, 21 Jul 1997, Teunis Peters wrote: > > > You're right, it IS easy..... providing you don't want any changes... > > [like 4(?) different optimizations for 6x86 and you don't want to run all > > of them] > > Huh? Boot parameters maybe? A run time tool like set6x86? Half a dozen > lines of assembler against a full kernel recompile each time you want > a change?!?
No - these affect things like memory page size in the linux memory manager + how memory pages are shared and organized. AFAIK this requires a recompile.
Here's a list (from the patch I use):(translations from docs and guesswork) [all cyrix] : No I/O recovery delays (rendered useless by branch prediction) [prolly would work on non-cyrix too] [6x86]: Avoid unnecessary locked cycles [useless with SMP] - locked areas are forced into CPU cache Allocate L1 cache lines on write misses ! may cause excessive memory use/slowdown : should speed system up if works Branch Target Buffer features - configures branch target prediction logic to better handle Linux ! not guaranteed to work let alone help VSPM (Variable Size Paging Mechanism) - large regions of memory can be mapped in one go. ! Known to be buggy with many 6x86's
There's prolly others in other patches too. These are not features that can be enabled outside of a kernel compile for the most part (especially VSPM and 'avoid unnecessary locked cycles') [I don't use most of these - just the I/O and locking optimizations]
> > Thanks to CPU-detection being a LITTLE behind (what, no K6 or 6x86? no > > MMX? HUH?????) [nevermind - I KNOW this is fixed now - just making a > > point].... we sorta may end up needing this... > > The current code is still lacking in CPU identification.
Wish I could help here.
> > FWIW - Can MMX be detected? Will it's PRESENCE be in /proc/cpuinfo? I'm > > planning on supporting it but I want to disable it if it isn't present.... > > Check the docs for any modern MMX cpu. It's in the CPUID flags.
But is CPUID available outside kernel?
[I don't have the time to try and find docs - 'sides I can only really handle html at this point and I know they're not in that form]. [I also don't have space - I'm too buzy trying to get some video solution together + database development + Java].
Have a pleasant week :) - Teunis
| |