Why the server shows less total memory compared to the physical memory installed
I have 2 guestOS of RHEL on VMware Virtual Center 2.5.0
Resource allocated to GuestOS of RHELA and RHELB identical.
Memory: 4608 MB
RHEL A
[root@RHELA ~]# free -m
total used free shared buffers cached
Mem: 4082 130 3952 0 12 32
-/+ buffers/cache: 85 3997
Swap: 2047 0 2047
dmesg:
BIOS-provided physical RAM map:
BIOS-e820: 0000000000000000 - 000000000009f800 (usable)
BIOS-e820: 000000000009f800 - 00000000000a0000 (reserved)
BIOS-e820: 00000000000ca000 - 00000000000cc000 (reserved)
BIOS-e820: 00000000000dc000 - 0000000000100000 (reserved)
BIOS-e820: 0000000000100000 - 00000000efef0000 (usable)
BIOS-e820: 00000000efef0000 - 00000000efeff000 (ACPI data)
BIOS-e820: 00000000efeff000 - 00000000eff00000 (ACPI NVS)
BIOS-e820: 00000000eff00000 - 00000000f0000000 (usable)
BIOS-e820: 00000000fec00000 - 00000000fec10000 (reserved)
BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
BIOS-e820: 00000000fffe0000 - 0000000100000000 (reserved)
BIOS-e820: 0000000100000000 - 0000000120000000 (usable)
...
x86 PAT enabled: cpu 0, old 0x0, new 0x7010600070106
original variable MTRRs
reg 0, base: 3840MB, range: 256MB, type UC
reg 1, base: 0GB, range: 4GB, type WB
reg 2, base: 4GB, range: 512MB, type WB
total RAM covered: 4352M
RHEL B
[root@RHELB]# free -m
total used free shared buffers cached
Mem: 4329 448 3880 0 145 136
-/+ buffers/cache: 166 4162
Swap: 2991 0 2991
dmesg:
BIOS-provided physical RAM map:
BIOS-e820: 0000000000000000 - 000000000009f000 (usable)
BIOS-e820: 000000000009f000 - 00000000000a0000 (reserved)
BIOS-e820: 00000000000ca000 - 00000000000cc000 (reserved)
BIOS-e820: 00000000000dc000 - 0000000000100000 (reserved)
BIOS-e820: 0000000000100000 - 00000000bfee0000 (usable)
BIOS-e820: 00000000bfee0000 - 00000000bfeff000 (ACPI data)
BIOS-e820: 00000000bfeff000 - 00000000bff00000 (ACPI NVS)
BIOS-e820: 00000000bff00000 - 00000000c0000000 (usable)
BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
BIOS-e820: 00000000fec00000 - 00000000fec10000 (reserved)
BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
BIOS-e820: 00000000fffe0000 - 0000000100000000 (reserved)
BIOS-e820: 0000000100000000 - 0000000160000000 (usable)
...
total RAM covered: 4608M
In RHEL A BIOS-e820: 0000000100000000 - 0000000120000000 (usable)[4608MB] and total RAM covered: 4352M
In RHEL B also resource allocated memory 4608MB, but: BIOS-e820: 0000000100000000 - 0000000160000000 (usable)[5632MB] and total RAM covered: 4608M
I found https://access.redhat.com/solutions/454133 but RHELA (4608-4082)/4608 = 11.4% , RHELB (4608-4329)/4608=6%.
Where RHEL A lost ~300MB memory?
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