4GB out of 8GB total reserved 64bit 12.04 why

Question

Can anyone explain why 50% of my ram is being reserved and for what? I do have two radeon 7990 cards but surely the ram is not reserved for them?

root@stan-desktop:/home/stan# cat /etc/issue
Ubuntu 12.04.3 LTS \n \l

root@stan-desktop:/home/stan# uname -a
Linux stan-desktop 3.8.0-35-generic #50~precise1-Ubuntu SMP Wed Dec 4 17:25:51 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
root@stan-desktop:/home/stan# cat /etc/issue^C
root@stan-desktop:/home/stan# cat /etc/issue
Ubuntu 12.04.3 LTS \n \l

root@stan-desktop:/home/stan# free -m
             total       used       free     shared    buffers     cached
Mem:          3912       1571       2341          0         81        625
-/+ buffers/cache:        863       3048
Swap:         8148          0       8148
root@stan-desktop:/home/stan# uname -a
Linux stan-desktop 3.8.0-35-generic #50~precise1-Ubuntu SMP Wed Dec 4 17:25:51 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
root@stan-desktop:/home/stan# lshw -c memory
  *-firmware              
       description: BIOS
       vendor: American Megatrends Inc.
       physical id: 0
       version: P1.50
       date: 10/12/2012
       size: 64KiB
       capacity: 4032KiB
       capabilities: pci upgrade shadowing cdboot bootselect socketedrom edd int13floppy1200 int13floppy720 int13floppy2880 int5printscreen int9keyboard int14serial int17printer acpi usb biosbootspecification
  *-cache:0
       description: L1 cache
       physical id: 5
       slot: L1-Cache
       size: 192KiB
       capacity: 192KiB
       clock: 1GHz (1.0ns)
       capabilities: pipeline-burst internal write-back unified
  *-cache:1
       description: L2 cache
       physical id: 6
       slot: L2-Cache
       size: 4MiB
       capacity: 4MiB
       clock: 1GHz (1.0ns)
       capabilities: pipeline-burst internal write-back unified
  *-cache:2
       description: L3 cache
       physical id: 7
       slot: L3-Cache
       size: 4MiB
       capacity: 4MiB
       clock: 1GHz (1.0ns)
       capabilities: pipeline-burst internal write-back unified
  *-memory
       description: System Memory
       physical id: f
       slot: System board or motherboard
       size: 8GiB
     *-bank:0
          description: DIMM DDR3 Synchronous 667 MHz (1.5 ns)
          product: PSD34G133381
          vendor: Undefined
          physical id: 0
          serial: 00000000
          slot: A1_DIMM0
          size: 4GiB
          width: 64 bits
          clock: 667MHz (1.5ns)
     *-bank:1
          description: DIMM Synchronous [empty]
          product: Array1_PartNumber1
          vendor: A1_Manufacturer1
          physical id: 1
          serial: A1_SerNum1
          slot: A1_DIMM1
     *-bank:2
          description: DIMM DDR3 Synchronous 667 MHz (1.5 ns)
          product: PSD34G133381
          vendor: Undefined
          physical id: 2
          serial: 00000000
          slot: A1_DIMM2
          size: 4GiB
          width: 64 bits
          clock: 667MHz (1.5ns)
     *-bank:3
          description: DIMM Synchronous [empty]
          product: Array1_PartNumber3
          vendor: A1_Manufacturer3
          physical id: 3
          serial: A1_SerNum3
          slot: A1_DIMM3
root@stan-desktop:/home/stan# dmesg | grep e820
[    0.000000] e820: BIOS-provided physical RAM map:
[    0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009ffff] usable
[    0.000000] BIOS-e820: [mem 0x0000000000100000-0x000000008e1e2fff] usable
[    0.000000] BIOS-e820: [mem 0x000000008e1e3000-0x000000008e4f5fff] reserved
[    0.000000] BIOS-e820: [mem 0x000000008e4f6000-0x000000008e8defff] ACPI NVS
[    0.000000] BIOS-e820: [mem 0x000000008e8df000-0x000000008ee31fff] reserved
[    0.000000] BIOS-e820: [mem 0x000000008ee32000-0x000000008ee32fff] usable
[    0.000000] BIOS-e820: [mem 0x000000008ee33000-0x000000008f038fff] ACPI NVS
[    0.000000] BIOS-e820: [mem 0x000000008f039000-0x000000008f452fff] usable
[    0.000000] BIOS-e820: [mem 0x000000008f453000-0x000000008f7f3fff] reserved
[    0.000000] BIOS-e820: [mem 0x000000008f7f4000-0x000000008f7fffff] usable
[    0.000000] BIOS-e820: [mem 0x00000000fec00000-0x00000000fec00fff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fec10000-0x00000000fec10fff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fec20000-0x00000000fec20fff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fed00000-0x00000000fed00fff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fed61000-0x00000000fed70fff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fed80000-0x00000000fed8ffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fef00000-0x00000000ffffffff] reserved
[    0.000000] BIOS-e820: [mem 0x0000000100001000-0x000000016effffff] usable
[    0.000000] e820: update [mem 0x00000000-0x0000ffff] usable ==> reserved
[    0.000000] e820: remove [mem 0x000a0000-0x000fffff] usable
[    0.000000] e820: last_pfn = 0x16f000 max_arch_pfn = 0x400000000
[    0.000000] e820: update [mem 0x8f800000-0xffffffff] usable ==> reserved
[    0.000000] e820: last_pfn = 0x8f800 max_arch_pfn = 0x400000000
[    0.000000] e820: [mem 0x8f800000-0xfebfffff] available for PCI devices
[    0.347889] e820: reserve RAM buffer [mem 0x8e1e3000-0x8fffffff]
[    0.347891] e820: reserve RAM buffer [mem 0x8ee33000-0x8fffffff]
[    0.347892] e820: reserve RAM buffer [mem 0x8f453000-0x8fffffff]
[    0.347893] e820: reserve RAM buffer [mem 0x8f800000-0x8fffffff]
[    0.347895] e820: reserve RAM buffer [mem 0x16f000000-0x16fffffff]
root@stan-desktop:/home/stan# cat /proc/meminfo
MemTotal:        4006400 kB
MemFree:         2397856 kB
Buffers:           83668 kB
Cached:           640776 kB
SwapCached:            0 kB
Active:           594800 kB
Inactive:         477904 kB
Active(anon):     349120 kB
Inactive(anon):      232 kB
Active(file):     245680 kB
Inactive(file):   477672 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:       8344572 kB
SwapFree:        8344572 kB
Dirty:                 0 kB
Writeback:             0 kB
AnonPages:        348256 kB
Mapped:           261108 kB
Shmem:              1096 kB
Slab:              96600 kB
SReclaimable:      65196 kB
SUnreclaim:        31404 kB
KernelStack:        3016 kB
PageTables:        24424 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:    10347772 kB
Committed_AS:    1839192 kB
VmallocTotal:   34359738367 kB
VmallocUsed:      387712 kB
VmallocChunk:   34359347964 kB
HardwareCorrupted:     0 kB
AnonHugePages:         0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:      362492 kB
DirectMap2M:     3807232 kB
DirectMap1G:           0 kB
root@stan-desktop:/home/stan#

I think it might be how your mobo expects the ram to be installed physically. From the output you posted it looks like the bios is reserving the ram. This might be similar: http://superuser.com/questions/56157/why-is-all-my-extra-ram-marked-as-hardware-reserved-in-windows-7 — amanthethy, Jan 15 '15 at 19:30

score 1 · Answer 1 · edited Apr 13 '17 at 12:23

I would not bother about Ubuntu using half of my RAM, as it is usually used to cache information to be able to access them very fast. So caching as much as possible (e.g. from your hard disk) is the best Ubuntu can do, as long as there is this much space left for other applications and no need to use the swap.
But if you are interested in which processes are occupying the memory, try top or htop which should give you an output similar to the windows task manager's processes-tab.
More infos: top description / list of monitoring tools

4GB out of 8GB total reserved 64bit 12.04 why

1 Answers1