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Ingo Molnar wrote:
> * Andi Kleen <ak@muc.de> wrote:
>
>
>>> Although I've not re-tested this today again, it used to help a bit to specify
>>>mem=3548M to decrease memory used by linux (tested with AGP card plugged in, when
>>>bios reported 3556MB RAM only).
>>>
>>> I found that removing the AGP based videoc card and using an old PCI based
>>>video card results in bios detecting 4072MB of RAM. But still, the machine was
>>>slow. I've tried to "cat >| /proc/mtrr" to alter the memory settings, but the
>>>result was only a partial speedup.
>>>
>>> I'm not sure how to convince linux kernel to run fast again.
>>
>>It's most likely a MTRR problem. Play more with them.
>
>
> in particular, try to create two small tables in the same format: one
> showing the e820 memory map as reported in your kernel log, and one
> showing the mtrr areas. If there is any e820 area that is not write-back
> cached via the mtrr mappings then that's the problem. You can also use
> "mem=exactmap,..." to fix up the memory map that the BIOS provides to
> Linux. Slowdowns are very often such MTRR problems. (perhaps the kernel
> should report RAM areas that are not covered by MTRR write-back?)
I've just extracted the requested info from the files I've put on web.
Here it is:
2.4.30-pre1-bk5 2.6.11-rc4-bk7
0000000000000000 - 000000000009fc00 (usable) + +
000000000009fc00 - 00000000000a0000 (reserved) + +
00000000000e8000 - 0000000000100000 (reserved) + +
0000000000100000 - 00000000de330000 (usable) + +
00000000de330000 - 00000000de340000 (ACPI data) + +
00000000de340000 - 00000000de3f0000 (ACPI NVS) + +
00000000de3f0000 - 00000000de400000 (reserved) + +
00000000ffb80000 - 0000000100000000 (reserved) + +
found SMP MP-table at 000ff780 + +
hm, page 000ff000 reserved twice. + - ???
hm, page 00100000 reserved twice. + - ???
hm, page 000f1000 reserved twice. + - ???
hm, page 000f2000 reserved twice. + - ???
2.4.30-pre1-bk5 2.6.11-rc4-bk7
reg00: base=0x00000000 ( 0MB), size=2048MB: write-back, count=1 + +
reg01: base=0x80000000 (2048MB), size=1024MB: write-back, count=1 + +
reg02: base=0xc0000000 (3072MB), size= 256MB: write-back, count=1 + +
reg03: base=0xd0000000 (3328MB), size= 128MB: write-back, count=1 + +
reg04: base=0xd8000000 (3456MB), size= 64MB: write-back, count=1 + +
reg05: base=0xdc000000 (3520MB), size= 32MB: write-back, count=1 + +
reg06: base=0xfe800000 (4072MB), size= 4MB: write-combining, count=1 + - !!!
reg06: base=0xf0000000 (3840MB), size= 128MB: write-combining, count=1 + +
The 4MB area should be AGP aperture, as it was set in BIOS to 4MB only
The files on web contain concatened infor from dmes, iomem, interrupts, mtrr, lspci:
http://www.natur.cuni.cz/~mmokrejs/tmp/4MB/2.4.30-pre1-bk5
http://www.natur.cuni.cz/~mmokrejs/tmp/4MB/2.6.11-rc4-bk7
So, 2.6 kernel does not see AGP aperture area. What to do next? ;)
Martin
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