Re: page reserved twice

From: michaelc (
Date: Wed Jul 04 2001 - 01:57:56 EST

Hello D.,

Wednesday, July 04, 2001, 8:19:27 AM, you wrote:

DS> I'm curious if there is any significance to this, which occurs at each
DS> reboot on an SMP system running noapic (sometimes Netscape manages to
DS> produce a hard lockup on the system, sometimes a core dump indicates NS
DS> had signal 7, bus error, in cases where it doesn't lock the system),
DS> 2.4.6-pre1 with XFS patches:

DS> kernel: BIOS-provided physical RAM map:
DS> kernel: BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
DS> kernel: BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
DS> kernel: BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)
DS> kernel: BIOS-e820: 0000000000100000 - 000000000ffe0000 (usable)
DS> kernel: BIOS-e820: 000000000ffe0000 - 000000000fff8000 (ACPI data)
DS> kernel: BIOS-e820: 000000000fff8000 - 0000000010000000 (ACPI NVS)
DS> kernel: Scan SMP from c0000000 for 1024 bytes.
DS> kernel: Scan SMP from c009fc00 for 1024 bytes.
DS> kernel: Scan SMP from c00f0000 for 65536 bytes.
DS> kernel: found SMP MP-table at 000faf50
DS> kernel: hm, page 000fa000 reserved twice.
DS> kernel: hm, page 000fb000 reserved twice.
DS> kernel: hm, page 000f4000 reserved twice.
DS> thanteros kernel: hm, page 000f5000 reserved twice.
DS> thanteros kernel: On node 0 totalpages: 65504
DS> thanteros kernel: zone(0): 4096 pages.
DS> kernel: zone(1): 61408 pages.
DS> kernel: zone(2): 0 pages.
DS> kernel: Intel MultiProcessor Specification v1.1
DS> kernel: Virtual Wire compatibility mode.
DS> kernel: OEM ID: _AMI_ Product ID: 840_CARMEL__ APIC at: 0xFEE00000

DS> Very similar messages seem to occur on a different machine with RH's
DS> 2.4.2 kernel, BX chipset, and IO-APIC enabled. The machine this is from
DS> has had this message on earlier kernels as well, none of which had XFS
DS> patches. What is the significance (or consequence) of pages reserved
DS> twice?
 I think that the message above doesn't matter with your nescape crash,
 When linux kernel boot, it reserve all usable low memory,for example
       kernel: BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
       kernel: BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)
 then kernel call find_smp_config to get MP configuration table if your machine
 is SMP, and the function will reserve the MP-table at 0xfa000,0xfb000, 0xf4000,
 and because these regions were reserved by kernel, so kernel would
 print the message, but it doesn't affect you system.

Best regards,

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