title: Embedded system: Where's my memory?
body: <p>I have an ARM based embedded system. I just bring up the kernel (2.6.34). Below are some command outputs. I am not able to account for whole of RAM (128 M).</p>
  
  <p>Kernel seems to be using 128 MB - 124368 kB = 6704 kB.</p>
  
  <pre><code>Cache = 1672 kB
  Slab = 3000 kB
  </code></pre>
  
  <p>But MemFree is only 100812 kB. How do I account for rest of the memory (around 18.5 MB)?</p>
  
  <p>Also what does Committed_AS value of 1512 kB indicate?</p>
  
  <pre><code># cat /proc/meminfo
  MemTotal:         124368 kB
  MemFree:          100812 kB
  Buffers:               0 kB
  Cached:             1672 kB
  SwapCached:            0 kB
  Active:             1692 kB
  Inactive:            284 kB
  Active(anon):        304 kB
  Inactive(anon):        0 kB
  Active(file):       1388 kB
  Inactive(file):      284 kB
  Unevictable:           0 kB
  Mlocked:               0 kB
  SwapTotal:             0 kB
  SwapFree:              0 kB
  Dirty:                 4 kB
  Writeback:             0 kB
  AnonPages:           328 kB
  Mapped:              856 kB
  Shmem:                 0 kB
  Slab:               3000 kB
  SReclaimable:       1116 kB
  SUnreclaim:         1884 kB
  KernelStack:         248 kB
  PageTables:           48 kB
  NFS_Unstable:          0 kB
  Bounce:                0 kB
  WritebackTmp:          0 kB
  CommitLimit:       62184 kB
  Committed_AS:       1512 kB
  VmallocTotal:     876544 kB
  VmallocUsed:        1848 kB
  VmallocChunk:     873908 kB
  
  
  
  # free
               total         used         free       shared      buffers
  Mem:        124368        23584       100784            0            0
  -/+ buffers:              23584       100784
  Swap:            0            0            0
  
  
  
  # lsmod
  Module                  Size  Used by    Not tainted
  
  
  
  # ps
    PID USER       VSZ STAT COMMAND
      1 0         1556 S    init
      2 0            0 SW   [kthreadd]
      3 0            0 SW   [ksoftirqd/0]
      4 0            0 SW   [watchdog/0]
      5 0            0 SW   [events/0]
      6 0            0 SW   [khelper]
     10 0            0 SW   [async/mgr]
    200 0            0 SW   [sync_supers]
    202 0            0 SW   [bdi-default]
    203 0            0 SW   [kblockd/0]
    209 0            0 SW   [ata/0]
    210 0            0 SW   [ata_aux]
    211 0            0 SW   [pxa2xx-spi.2]
    218 0            0 SW   [khubd]
    221 0            0 SW   [kseriod]
    234 0            0 SW   [kmmcd]
    253 0            0 SW   [rpciod/0]
    261 0            0 SW   [khungtaskd]
    262 0            0 SW   [kswapd0]
    264 0            0 SW   [aio/0]
    265 0            0 SW   [nfsiod]
    267 0            0 SW   [crypto/0]
    414 0            0 SW   [mtdblockd]
    457 0            0 SW   [ubi_bgt0d]
    537 0            0 SW   [usbhid_resumer]
    563 0            0 SW   [ubifs_bgt0_0]
    581 0         1556 S    telnetd -l /bin/sh
    586 0         1948 S &lt;  udevd -d
   2956 0         1560 S    -/bin/sh
   3986 0            0 SW   [flush-ubifs_0_0]
   3990 0         4216 R    ps
  </code></pre>