Clarification: Is CONFIG_HIGHMEM64G supposed to be set for 64bit Ubuntu Kernels or not?
Brendan Grainger
brendan at moto-research.com
Thu Oct 29 14:14:11 UTC 2009
Hi All,
We're running Xen enabled Hardy LTS 8.04 on an 8Gb ASUS P5QL VM
machine. We are finding that with memory remapping off the OS does not
see the whole 8Gb, but with memory remapping on it sees 8Gb. I have no
idea really, but I thought that memory remapping only applied to PAE
32bit linux. I've seen various posts regarding the CONFIG_HIGHMEM64G
setting be on in order for Ubuntu to see > 4Gb, but am confused as to
whether this applies only to PAE enabled 32bit Ubuntu. Is this setting
required for 64 bit ubuntu also? On our build it is not set:
root@?????:/boot# grep CONFIG_HIGHMEM64G config-2.6.24-2*
root@?????:/boot#
I've put the relevant bits of free -m and lshw below.
Thanks
Brendan
Further details:
# uname -a:
Linux wkr05 2.6.24-25-xen #1 SMP Tue Oct 20 08:47:34 UTC 2009 x86_64
GNU/Linux
# free -m with memory remapping on:
# free -m
total used free shared buffers
cached
Mem: 7833 350 7483 0 5
62
-/+ buffers/cache: 281 7551
Swap: 12401 0 12401
# free -m with memory remapping off:
# free -m
total used free shared buffers
cached
Mem: 3104 255 2848 0 4
60
-/+ buffers/cache: 190 2913
Swap: 12401 0 12401
# Relevant bit of lshw
# lshw
*-cpu:0
product: Intel(R) Core(TM)2 CPU 6400 @ 2.13GHz
vendor: Intel Corp.
physical id: 1
bus info: cpu at 0
width: 64 bits
capabilities: fpu fpu_exception wp de tsc msr pae mce cx8
apic sep mtrr mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss
ht tm pbe syscall nx x86-64 constant_tsc arch_perfmon pebs bts
rep_good pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm
*-cpu:1
product: Intel(R) Core(TM)2 CPU 6400 @ 2.13GHz
vendor: Intel Corp.
physical id: 2
bus info: cpu at 1
width: 64 bits
capabilities: fpu fpu_exception wp de tsc msr pae mce cx8
apic sep mtrr mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss
ht tm pbe syscall nx x86-64 constant_tsc arch_perfmon pebs bts
rep_good pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm
*-memory
description: System Memory
physical id: 31
slot: System board or motherboard
size: 8GiB
*-bank:0
description: DIMM Synchronous 800 MHz (1.2 ns)
product: ModulePartNumber00
vendor: Manufacturer00
physical id: 0
serial: SerNum00
slot: DIMM0
size: 2GiB
width: 64 bits
clock: 800MHz (1.2ns)
*-bank:1
description: DIMM Synchronous 800 MHz (1.2 ns)
product: ModulePartNumber01
vendor: Manufacturer01
physical id: 1
serial: SerNum01
slot: DIMM1
size: 2GiB
width: 64 bits
clock: 800MHz (1.2ns)
*-bank:2
description: DIMM Synchronous 800 MHz (1.2 ns)
product: ModulePartNumber02
vendor: Manufacturer02
physical id: 2
serial: SerNum02
slot: DIMM2
size: 2GiB
width: 64 bits
clock: 800MHz (1.2ns)
*-bank:3
description: DIMM Synchronous 800 MHz (1.2 ns)
product: ModulePartNumber03
vendor: Manufacturer03
physical id: 3
serial: SerNum03
slot: DIMM3
size: 2GiB
width: 64 bits
clock: 800MHz (1.2ns)
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