经过几个月的正常工作后，我安装的 Centos 7 的 BIOS 突然将错误的内存量映射到内核。我安装了 8 GB RAM，而 SO 仅映射 3.2 GB RAM。我不明白为什么。
这是我认为值得关注的所有信息，但如果您需要更多信息，请告诉我。
关于硬件：
CPU: AMD Phenom(tm) 9550 Quad-Core Processor
Motherboard: GA-MA780G-UD3H
Rare Hardware: MegaRAID SAS 2008 [Falcon]
dmesg | grep -i 内存
[ 0.000000] BIOS-e801: [mem 0x0000000000000000-0x000000000009efff] usable
[ 0.000000] BIOS-e801: [mem 0x0000000000100000-0x00000000cdecffff] usable
[ 0.000000] e820: update [mem 0x00000000-0x00000fff] usable ==> reserved
[ 0.000000] e820: remove [mem 0x000a0000-0x000fffff] usable
[ 0.000000] e820: update [mem 0xcff00000-0xffffffff] usable ==> reserved
[ 0.000000] found SMP MP-table at [mem 0x000f57c0-0x000f57cf] mapped at [fffffffffd2007c0]
[ 0.000000] Base memory trampoline at [ffff880000098000] 98000 size 24576
[ 0.000000] RAMDISK: [mem 0x3529f000-0x36947fff]
[ 0.000000] Faking a node at [mem 0x0000000000000000-0x00000000cdecffff]
[ 0.000000] NODE_DATA(0) allocated [mem 0xcdeae000-0xcdecffff]
[ 0.000000] crashkernel: memory value expected
[ 0.000000] DMA [mem 0x0000000000001000-0x0000000000ffffff]
[ 0.000000] DMA32 [mem 0x0000000001000000-0x00000000cdecffff]
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000000001000-0x000000000009efff]
[ 0.000000] node 0: [mem 0x0000000000100000-0x00000000cdecffff]
[ 0.000000] Initmem setup node 0 [mem 0x0000000000001000-0x00000000cdecffff]
[ 0.000000] DMA zone: 64 pages used for memmap
[ 0.000000] DMA32 zone: 13116 pages used for memmap
[ 0.000000] PM: Registered nosave memory: [mem 0x00000000-0x00000fff]
[ 0.000000] PM: Registered nosave memory: [mem 0x0009f000-0x000fffff]
[ 0.000000] e820: [mem 0xcded0000-0xffffffff] available for PCI devices
[ 0.007556] Freeing SMP alternatives memory: 32K
[ 0.028268] Fam 10h mmconf [mem 0xe0000000-0xe00fffff]
[ 0.028268] bus: 00 [mem 0x000a0000-0x000bffff]
[ 0.028268] bus: 00 [mem 0xd0000000-0xdfffffff]
[ 0.028268] bus: 00 [mem 0xe0600000-0xffffffff]
[ 0.028268] bus: 00 [mem 0xe0100000-0xe05fffff]
[ 0.028268] bus: 00 [mem 0x230000000-0xfcffffffff]
[ 0.028268] PCI: MMCONFIG for domain 0000 [bus 00-ff] at [mem 0xe0000000-0xefffffff] (base 0xe0000000)
[ 0.038526] PCI: MMCONFIG for domain 0000 [bus 00-ff] at [mem 0xe0000000-0xefffffff] (base 0xe0000000)
[ 0.039286] PCI: MMCONFIG at [mem 0xe0000000-0xefffffff] reserved in ACPI motherboard resources
[ 0.046039] pci_bus 0000:00: root bus resource [mem 0x000a0000-0x000bffff window]
[ 0.046040] pci_bus 0000:00: root bus resource [mem 0x000c0000-0x000dffff window]
[ 0.046042] pci_bus 0000:00: root bus resource [mem 0xd0000000-0xfebfffff window]
[ 0.046769] pci 0000:00:11.0: reg 0x24: [mem 0xfe02f000-0xfe02f3ff]
[ 0.046916] pci 0000:00:12.0: reg 0x10: [mem 0xfe02e000-0xfe02efff]
[ 0.047077] pci 0000:00:12.1: reg 0x10: [mem 0xfe02d000-0xfe02dfff]
[ 0.047240] pci 0000:00:12.2: reg 0x10: [mem 0xfe02c000-0xfe02c0ff]
[ 0.047432] pci 0000:00:13.0: reg 0x10: [mem 0xfe02b000-0xfe02bfff]
[ 0.047588] pci 0000:00:13.1: reg 0x10: [mem 0xfe02a000-0xfe02afff]
[ 0.047749] pci 0000:00:13.2: reg 0x10: [mem 0xfe029000-0xfe0290ff]
[ 0.048567] pci 0000:00:14.5: reg 0x10: [mem 0xfe028000-0xfe028fff]
[ 0.049170] pci 0000:01:00.0: reg 0x10: [mem 0xd0000000-0xdfffffff 64bit pref]
[ 0.049179] pci 0000:01:00.0: reg 0x18: [mem 0xfd7e0000-0xfd7effff 64bit]
[ 0.049197] pci 0000:01:00.0: reg 0x30: [mem 0x00000000-0x0001ffff pref]
[ 0.049293] pci 0000:01:00.1: reg 0x10: [mem 0xfd7fc000-0xfd7fffff 64bit]
[ 0.052017] pci 0000:00:02.0: bridge window [mem 0xfd700000-0xfd7fffff]
[ 0.052020] pci 0000:00:02.0: bridge window [mem 0xd0000000-0xdfffffff 64bit pref]
[ 0.052087] pci 0000:02:00.0: reg 0x14: [mem 0xfdffc000-0xfdffffff 64bit]
[ 0.052098] pci 0000:02:00.0: reg 0x1c: [mem 0xfdf80000-0xfdfbffff 64bit]
[ 0.052112] pci 0000:02:00.0: reg 0x30: [mem 0x00000000-0x0001ffff pref]
[ 0.055016] pci 0000:00:04.0: bridge window [mem 0xfdf00000-0xfdffffff]
[ 0.055019] pci 0000:00:04.0: bridge window [mem 0xfde00000-0xfdefffff 64bit pref]
[ 0.055100] pci 0000:03:00.0: reg 0x18: [mem 0xfddff000-0xfddfffff 64bit]
[ 0.055112] pci 0000:03:00.0: reg 0x20: [mem 0xfdcfc000-0xfdcfffff 64bit pref]
[ 0.058021] pci 0000:00:09.0: bridge window [mem 0xfdd00000-0xfddfffff]
[ 0.058024] pci 0000:00:09.0: bridge window [mem 0xfdc00000-0xfdcfffff 64bit pref]
[ 0.058104] pci 0000:04:00.0: reg 0x18: [mem 0xfdaff000-0xfdafffff 64bit pref]
[ 0.058116] pci 0000:04:00.0: reg 0x20: [mem 0xfdae0000-0xfdaeffff 64bit pref]
[ 0.058125] pci 0000:04:00.0: reg 0x30: [mem 0x00000000-0x0000ffff pref]
[ 0.061019] pci 0000:00:0a.0: bridge window [mem 0xfdb00000-0xfdbfffff]
[ 0.061022] pci 0000:00:0a.0: bridge window [mem 0xfda00000-0xfdafffff 64bit pref]
[ 0.061100] pci 0000:00:14.4: bridge window [mem 0xfd900000-0xfd9fffff]
[ 0.061104] pci 0000:00:14.4: bridge window [mem 0xfd800000-0xfd8fffff pref]
[ 0.061109] pci 0000:00:14.4: bridge window [mem 0x000a0000-0x000bffff window] (subtractive decode)
[ 0.061111] pci 0000:00:14.4: bridge window [mem 0x000c0000-0x000dffff window] (subtractive decode)
[ 0.061112] pci 0000:00:14.4: bridge window [mem 0xd0000000-0xfebfffff window] (subtractive decode)
[ 0.062580] pci 0000:01:00.0: vgaarb: VGA device added: decodes=io+mem,owns=io+mem,locks=none
[ 0.071632] e820: reserve RAM buffer [mem 0x0009f000-0x0009ffff]
[ 0.071634] e820: reserve RAM buffer [mem 0xcded0000-0xcfffffff]
[ 0.089630] pnp 00:01: disabling [mem 0x00000000-0x00000fff window] because it overlaps 0000:01:00.0 BAR 6 [mem 0x00000000-0x0001ffff pref]
[ 0.089635] pnp 00:01: disabling [mem 0x00000000-0x00000fff window disabled] because it overlaps 0000:02:00.0 BAR 6 [mem 0x00000000-0x0001ffff pref]
[ 0.089640] pnp 00:01: disabling [mem 0x00000000-0x00000fff window disabled] because it overlaps 0000:04:00.0 BAR 6 [mem 0x00000000-0x0000ffff pref]
[ 0.089699] system 00:01: [mem 0xfee00400-0xfee00fff window] has been reserved
[ 0.090378] system 00:03: [mem 0xe0000000-0xefffffff] has been reserved
[ 0.090592] system 00:04: [mem 0x000d7c00-0x000d7fff] has been reserved
[ 0.090595] system 00:04: [mem 0x000f0000-0x000f7fff] could not be reserved
[ 0.090597] system 00:04: [mem 0x000f8000-0x000fbfff] could not be reserved
[ 0.090598] system 00:04: [mem 0x000fc000-0x000fffff] could not be reserved
[ 0.090600] system 00:04: [mem 0xcfee0000-0xcfefffff] could not be reserved
[ 0.090602] system 00:04: [mem 0xffff0000-0xffffffff] has been reserved
[ 0.090603] system 00:04: [mem 0x00000000-0x0009ffff] could not be reserved
[ 0.090605] system 00:04: [mem 0x00100000-0xcfedffff] could not be reserved
[ 0.090607] system 00:04: [mem 0xfec00000-0xfec00fff] could not be reserved
[ 0.090609] system 00:04: [mem 0xfee00000-0xfee00fff] could not be reserved
[ 0.090610] system 00:04: [mem 0xfff80000-0xfffeffff] has been reserved
[ 0.097979] pci 0000:01:00.0: BAR 6: assigned [mem 0xfd700000-0xfd71ffff pref]
[ 0.097988] pci 0000:00:02.0: bridge window [mem 0xfd700000-0xfd7fffff]
[ 0.097990] pci 0000:00:02.0: bridge window [mem 0xd0000000-0xdfffffff 64bit pref]
[ 0.097994] pci 0000:02:00.0: BAR 6: assigned [mem 0xfdf00000-0xfdf1ffff pref]
[ 0.098000] pci 0000:00:04.0: bridge window [mem 0xfdf00000-0xfdffffff]
[ 0.098009] pci 0000:00:04.0: bridge window [mem 0xfde00000-0xfdefffff 64bit pref]
[ 0.098017] pci 0000:00:09.0: bridge window [mem 0xfdd00000-0xfddfffff]
[ 0.098019] pci 0000:00:09.0: bridge window [mem 0xfdc00000-0xfdcfffff 64bit pref]
[ 0.098023] pci 0000:04:00.0: BAR 6: assigned [mem 0xfdb00000-0xfdb0ffff pref]
[ 0.098028] pci 0000:00:0a.0: bridge window [mem 0xfdb00000-0xfdbfffff]
[ 0.098030] pci 0000:00:0a.0: bridge window [mem 0xfda00000-0xfdafffff 64bit pref]
[ 0.098041] pci 0000:00:14.4: bridge window [mem 0xfd900000-0xfd9fffff]
[ 0.098044] pci 0000:00:14.4: bridge window [mem 0xfd800000-0xfd8fffff pref]
[ 0.098056] pci_bus 0000:00: resource 6 [mem 0x000a0000-0x000bffff window]
[ 0.098057] pci_bus 0000:00: resource 7 [mem 0x000c0000-0x000dffff window]
[ 0.098059] pci_bus 0000:00: resource 8 [mem 0xd0000000-0xfebfffff window]
[ 0.098062] pci_bus 0000:01: resource 1 [mem 0xfd700000-0xfd7fffff]
[ 0.098063] pci_bus 0000:01: resource 2 [mem 0xd0000000-0xdfffffff 64bit pref]
[ 0.098067] pci_bus 0000:02: resource 1 [mem 0xfdf00000-0xfdffffff]
[ 0.098068] pci_bus 0000:02: resource 2 [mem 0xfde00000-0xfdefffff 64bit pref]
[ 0.098071] pci_bus 0000:03: resource 1 [mem 0xfdd00000-0xfddfffff]
[ 0.098073] pci_bus 0000:03: resource 2 [mem 0xfdc00000-0xfdcfffff 64bit pref]
[ 0.098075] pci_bus 0000:04: resource 1 [mem 0xfdb00000-0xfdbfffff]
[ 0.098077] pci_bus 0000:04: resource 2 [mem 0xfda00000-0xfdafffff 64bit pref]
[ 0.098080] pci_bus 0000:05: resource 1 [mem 0xfd900000-0xfd9fffff]
[ 0.098082] pci_bus 0000:05: resource 2 [mem 0xfd800000-0xfd8fffff pref]
[ 0.098086] pci_bus 0000:05: resource 6 [mem 0x000a0000-0x000bffff window]
[ 0.098087] pci_bus 0000:05: resource 7 [mem 0x000c0000-0x000dffff window]
[ 0.098089] pci_bus 0000:05: resource 8 [mem 0xd0000000-0xfebfffff window]
[ 0.440156] pci 0000:01:00.0: Video device with shadowed ROM at [mem 0x000c0000-0x000dffff]
[ 0.889247] Freeing initrd memory: 23204K
[ 1.415893] Non-volatile memory driver v1.3
[ 1.416846] ehci-pci 0000:00:12.2: irq 17, io mem 0xfe02c000
[ 1.423652] ehci-pci 0000:00:13.2: irq 19, io mem 0xfe029000
[ 1.430547] ohci-pci 0000:00:12.0: irq 16, io mem 0xfe02e000
[ 1.486520] ohci-pci 0000:00:12.1: irq 16, io mem 0xfe02d000
[ 1.542513] ohci-pci 0000:00:13.0: irq 18, io mem 0xfe02b000
[ 1.598498] ohci-pci 0000:00:13.1: irq 18, io mem 0xfe02a000
[ 1.654502] ohci-pci 0000:00:14.5: irq 18, io mem 0xfe028000
[ 1.724405] Freeing unused kernel memory: 2232K
[ 1.724676] Freeing unused kernel memory: 132K
[ 1.726622] Freeing unused kernel memory: 544K
[ 2.019715] resource sanity check: requesting [mem 0x000c0000-0x000dffff], which spans more than pnp 00:04 [mem 0x000d7c00-0x000d7fff]
[ 2.020483] [TTM] Zone kernel: Available graphics memory: 1651458 kiB
[ 2.020515] [drm] radeon: 256M of VRAM memory ready
[ 2.020516] [drm] radeon: 512M of GTT memory ready.
uname -a
Linux <host> 4.14.0-1.el7.elrepo.x86_64 #1 SMP Sun Nov 12 20:21:04 EST 2017 x86_64 x86_64 x86_64 GNU/Linux
lshw-短| grep '系统内存'
/0/29 memory 8GiB System Memory
自由-m
total used free shared buff/cache available
Mem: 3225 155 95 8 2974 2838
Swap: 8191 0 8191
lshw -c 内存
*-firmware
description: BIOS
vendor: Award Software International, Inc.
physical id: 0
version: F5
date: 10/08/2009
size: 128KiB
capacity: 960KiB
capabilities: isa pci pnp apm upgrade shadowing cdboot bootselect socketedrom edd int13floppy360 int13floppy1200 int13floppy720 int13floppy2880 int5printscreen int9keyboard int14serial int17printer int10video acpi usb agp ls120boot zipboot biosbootspecification
*-cache:0
description: L1 cache
physical id: a
slot: Internal Cache
size: 128KiB
capacity: 128KiB
capabilities: synchronous internal write-back
configuration: level=1
*-cache:1
description: L2 cache
physical id: c
slot: External Cache
size: 512KiB
capacity: 512KiB
capabilities: synchronous internal write-back
configuration: level=2
*-cache
description: L1 cache
physical id: b
slot: Internal Cache
size: 128KiB
capacity: 128KiB
capabilities: synchronous internal write-back
configuration: level=1
*-memory
description: System Memory
physical id: 29
slot: System board or motherboard
size: 8GiB
*-bank:0
description: DIMM 800 MHz (1.2 ns)
product: None
vendor: None
physical id: 0
serial: None
slot: A0
size: 2GiB
width: 64 bits
clock: 800MHz (1.2ns)
*-bank:1
description: DIMM 800 MHz (1.2 ns)
product: None
vendor: None
physical id: 1
serial: None
slot: A1
size: 2GiB
width: 64 bits
clock: 800MHz (1.2ns)
*-bank:2
description: DIMM 800 MHz (1.2 ns)
product: None
vendor: None
physical id: 2
serial: None
slot: A2
size: 2GiB
width: 64 bits
clock: 800MHz (1.2ns)
*-bank:3
description: DIMM 800 MHz (1.2 ns)
product: None
vendor: None
physical id: 3
serial: None
slot: A3
size: 2GiB
width: 64 bits
clock: 800MHz (1.2ns)
猫 /proc/meminfo | grep 直接
DirectMap4k: 95040 kB
DirectMap2M: 2230272 kB
DirectMap1G: 2097152 kB