Memory used but i can't see process that used it (Debian)

Question

Here is my problem:

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  

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?

Thanks for answer.

Answer 1

www.linuxatemyram.com

It's too good of a site to ruin by copy/pasting the entire contents here.