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HIGHMEM

DISCUSSION Nagy Tibor 3 participants 3 messages Apr 15, 2003

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Nagy Tibor

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Hi,

We have two Dell Poweredge servers, an older one (PowerEdge 6300) and a newer one (PowerEdge 6400). Both servers have 4GB RAM, but the Linux kernel uses about 500MB less memory in the newer machine.

See /var/log/boot.msg on the old one:

<4>Linux version 2.4.20 (root@dell632) (gcc version 2.95.3 20010315 (SuSE)) #4 SMP Fri Jan 10 12:07:00 CET 2003 <6>BIOS-provided physical RAM map:
<4> BIOS-e820: 0000000000000000 - 00000000000a0000 (usable) <4> BIOS-e820: 0000000000100000 - 00000000fbffe000 (usable) <4> BIOS-e820: 00000000fbffe000 - 00000000fc000000 (reserved) <4> BIOS-e820: 00000000fec00000 - 00000000fec10000 (reserved) <4> BIOS-e820: 00000000fee00000 - 00000000fee10000 (reserved) <4> BIOS-e820: 00000000fff80000 - 0000000100000000 (reserved) <5>3135MB HIGHMEM available.
<5>896MB LOWMEM available.

and on the new one:

<4>Linux version 2.4.20 (root@alfa) (gcc version 2.95.3 20010315 (SuSE)) #10 SMP Fri Mar 28 15:40:45 CET 2003
<6>BIOS-provided physical RAM map:
<4> BIOS-e820: 0000000000000000 - 00000000000a0000 (usable) <4> BIOS-e820: 0000000000100000 - 00000000dfff0000 (usable) <4> BIOS-e820: 00000000dfff0000 - 00000000dfffec00 (ACPI data) <4> BIOS-e820: 00000000dfffec00 - 00000000dffff000 (reserved) <4> BIOS-e820: 00000000fec00000 - 00000000fec10000 (reserved) <4> BIOS-e820: 00000000fee00000 - 00000000fee10000 (reserved) <4> BIOS-e820: 00000000fff80000 - 0000000100000000 (reserved) <5>2687MB HIGHMEM available.
<5>896MB LOWMEM available.

There is a big hole between 00000000dffff000 and 00000000fec00000, which is not used on the new machine. What can I do?

Thanks for your help.

Tibor

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Tibor Nagy
E-mail: [email protected]
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#1 lore raw
Quoted 9 lines · Nagy Tibor

<6>BIOS-provided physical RAM map:
<4> BIOS-e820: 0000000000000000 - 00000000000a0000 (usable) <4> BIOS-e820: 0000000000100000 - 00000000fbffe000 (usable) <4> BIOS-e820: 00000000fbffe000 - 00000000fc000000 (reserved) <4> BIOS-e820: 00000000fec00000 - 00000000fec10000 (reserved) <4> BIOS-e820: 00000000fee00000 - 00000000fee10000 (reserved) <4> BIOS-e820: 00000000fff80000 - 0000000100000000 (reserved) <5>3135MB HIGHMEM available.
<5>896MB LOWMEM available.

[...]

Quoted 4 lines

<6>BIOS-provided physical RAM map:
<4> BIOS-e820: 0000000000000000 - 00000000000a0000 (usable) <4> BIOS-e820: 0000000000100000 - 00000000dfff0000 (usable) <4> BIOS-e820: 00000000dfff0000 - 00000000dfffec00 (ACPI data)

Quoted 8 lines

<4> BIOS-e820: 00000000dfffec00 - 00000000dffff000 (reserved) <4> BIOS-e820: 00000000fec00000 - 00000000fec10000 (reserved) <4> BIOS-e820: 00000000fee00000 - 00000000fee10000 (reserved) <4> BIOS-e820: 00000000fff80000 - 0000000100000000 (reserved) <5>2687MB HIGHMEM available.
<5>896MB LOWMEM available.
There is a big hole between 00000000dffff000 and 00000000fec00000, which is not used on the new machine. What can I do?

Presumably that was lost to ACPI. The hole between 0xdffff000 and 0xfec00000 appears to not be covered by the e820.

Try turning ACPI off in your .config since there's something that looks relevant to it different between 2.4 and 2.5. You also might want to follow up with .config's just in case. I'll look at 2.5's e820 stuff, but no promises.

-- wli

#2 lore raw
In reply to Nagy Tibor
Quoted 5 lines · Nagy Tibor

There is a big hole between 00000000dffff000 and 00000000fec00000, which is not used on the new machine. What can I do?

You might also try making sure you have the latest bios, and try
turning off acpi in the bios.

Signature · 4 lines
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