title: Memory used but i can't see process that used it (Debian)
body: <p>Here is my problem:</p>
  
  <pre><code>top - 11:32:47 up 22:20,  2 users,  load average: 0.03, 0.72, 1.27
  Tasks: 112 total,   1 running, 110 sleeping,   1 stopped,   0 zombie
  Cpu(s):  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
  Mem:   8193844k total,  7508292k used,   685552k free,    80636k buffers
  Swap:  2102456k total,    15472k used,  2086984k free,  7070220k cached
  
    PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                                                                                                                                                                                           
  28555 root      20   0 57424  38m 1492 S    0  0.5   0:06.38 bash                                                                                                                                                                                                              
  28900 root      20   0 39488 7732 3176 T    0  0.1   0:03.12 python                                                                                                                                                                                                            
  28553 root      20   0 72132 5052 2600 S    0  0.1   0:00.22 sshd                                                                                                                                                                                                              
  28859 root      20   0 70588 3424 2584 S    0  0.0   0:00.06 sshd                                                                                                                                                                                                              
  29404 root      20   0 70448 3320 2600 S    0  0.0   0:00.06 sshd                                                                                                                                                                                                              
  28863 root      20   0 42624 2188 1472 S    0  0.0   0:00.02 sftp-server                                                                                                                                                                                                       
  29406 root      20   0 19176 1984 1424 S    0  0.0   0:00.00 bash                                                                                                                                                                                                              
   2854 root      20   0  115m 1760  488 S    0  0.0   5:37.02 rsyslogd                                                                                                                                                                                                          
  29410 root      20   0 19064 1400 1016 R    0  0.0   0:05.14 top                                                                                                                                                                                                               
   3111 ntp       20   0 22484  604  460 S    0  0.0  10:26.79 ntpd                                                                                                                                                                                                              
   3134 proftpd   20   0 64344  452  280 S    0  0.0   6:29.16 proftpd                                                                                                                                                                                                           
   2892 root      20   0 49168  356  232 S    0  0.0   0:31.58 sshd                                                                                                                                                                                                              
      1 root      20   0 27388  284  132 S    0  0.0   0:01.38 init                                                                                                                                                                                                              
   3121 root      20   0  4308  248  172 S    0  0.0   0:16.48 mdadm  
  </code></pre>
  
  <p>As you can see 7.5 GB of memory is used, but there is no process that use it.
  How it can be, and how to fix this?</p>
  
  <p>Thanks for answer.</p>