36 bit MTRRs, Re: test10-pre1 problems on 4-way SuperServer8050

From: Boszormenyi Zoltan (zboszor@externet.hu)
Date: Wed Oct 11 2000 - 10:39:07 EST


On Wed, 11 Oct 2000, Tigran Aivazian wrote:
> I will continue to narrow down by removing some things (like mtrr) from
> the equation. Rik, the problem is that when one enables PAE (or just
> highmem-4G) support on a 4-way 6G RAM machine becomes 38-40 times slower.

Will you please try this patch? This is almost the same as I
sent to you before, it is just against 2.4.0-test10-pre1 and
it lacks the corrections to e.g. the frame buffer drivers.

I am now running test10-pre1 with this patch and:

---------------------------------------------------------
[root@localhost /root]# cd /proc
[root@localhost /proc]# cat mtrr
reg00: base=0x00000000 ( 0MB), size= 128MB: write-back, count=1
reg05: base=0xe2000000 (3616MB), size= 32MB: write-combining, count=1
[root@localhost /proc]# echo "base=0x200000000 size=0x100000000 type=write-combining" >mtrr
[root@localhost /proc]# cat mtrr
reg00: base=0x00000000 ( 0MB), size= 128MB: write-back, count=1
reg01: base=0x00200000000 ( 8192MB), size= 4096MB: write-combining, count=1
reg05: base=0xe2000000 (3616MB), size= 32MB: write-combining, count=1
----------------------------------------------------------

This is on a dual P-III machine with 128 MB memory.
If it causes problems on Athlons then change the line

#define AMD_OR_MASK (0xfffff000UL)

to

#define AMD_OR_MASK (INTEL_OR_MASK)

and recompile and tell me what happens. Also, I would like to hear
reports from non-Intel (Cyrix, etc.) and older AMD machines.
I do not have my Cyrix 6x86MX anymore but this scheme worked on that.

Regards,
Zoltan Boszormenyi



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