Re: page reserved twice

From: michaelc (
Date: Wed Jul 04 2001 - 02:02:04 EST

Hello D.,

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

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, so it doesn't cause any problem on your machine.


Best regards,
 michael chen                  

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