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SubjectDoes Linux have plan to support memory hole remapping?
Hi experts,

I ask this because I run kernel 2.6.25-rc8 on a x64 system with 32GB
physical memory, and kernel only use (32GB-512MB) physical memory. See
below related information:
E820 table:
BIOS-provided physical RAM map:
BIOS-e820: 0000000000000000 - 0000000000098c00 (usable)
BIOS-e820: 0000000000098c00 - 00000000000a0000 (reserved)
BIOS-e820: 00000000000e6000 - 0000000000100000 (reserved)
BIOS-e820: 0000000000100000 - 00000000dffa0000 (usable)
BIOS-e820: 00000000dffae000 - 00000000dffb0000 type 9
BIOS-e820: 00000000dffb0000 - 00000000dffbe000 (ACPI data)
BIOS-e820: 00000000dffbe000 - 00000000dfff0000 (ACPI NVS)
BIOS-e820: 00000000dfff0000 - 00000000dfffe000 (reserved)
BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
BIOS-e820: 00000000fec00000 - 00000000fec01000 (reserved)
BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
BIOS-e820: 00000000ff700000 - 0000000100000000 (reserved)
BIOS-e820: 0000000100000000 - 0000000820000000 (usable)

/proc/mtrr:
reg00: base=0x00000000 ( 0MB), size=32768MB: write-back, count=1
reg01: base=0x800000000 (32768MB), size= 512MB: write-back, count=1
reg02: base=0xe0000000 (3584MB), size= 512MB: uncachable, count=1

/proc/meminfo:
MemTotal: 33010240 kB
MemFree: 32715924 kB
Buffers: 1624 kB
Cached: 31412 kB
SwapCached: 0 kB
Active: 22348 kB
Inactive: 19728 kB
SwapTotal: 0 kB
SwapFree: 0 kB
Dirty: 0 kB
Writeback: 0 kB
AnonPages: 9120 kB
Mapped: 6408 kB
Slab: 24828 kB
SReclaimable: 8004 kB
SUnreclaim: 16824 kB
PageTables: 1296 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
CommitLimit: 16505120 kB
Committed_AS: 16556 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 73524 kB
VmallocChunk: 34359664507 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB

As we can see from above information that the physical memory in system
is 32768MB(32GB). However OS is only using about
(32768-512)MB(MemTotal: 33010240 kB). Does this mean that this
linux kernel can't use the physical memory remapped
from (4G-512M, 4G) to (32G, 32G+512M)?

Thanks,
Forrest


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