con free -m vedo questo

codice:
             total       used       free     shared    buffers     cached
Mem:           993        528        465          0         39        380
-/+ buffers/cache:        108        885
Swap:         2911

e con top vedo questo

codice:
  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
 6683 root      20   0  2528 1168  904 R  0.3  0.1   0:00.01 top
    1 root      20   0  2756 1572 1164 S  0.0  0.2   0:00.38 init
    2 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kthreadd
    3 root      RT   0     0    0    0 S  0.0  0.0   0:00.00 migration/0
    4 root      20   0     0    0    0 S  0.0  0.0   0:00.00 ksoftirqd/0
    5 root      RT   0     0    0    0 S  0.0  0.0   0:00.00 watchdog/0
    6 root      20   0     0    0    0 S  0.0  0.0   0:00.25 events/0
    7 root      20   0     0    0    0 S  0.0  0.0   0:00.00 cpuset
    8 root      20   0     0    0    0 S  0.0  0.0   0:00.00 khelper
    9 root      20   0     0    0    0 S  0.0  0.0   0:00.00 netns
   10 root      20   0     0    0    0 S  0.0  0.0   0:00.00 async/mgr
   11 root      20   0     0    0    0 S  0.0  0.0   0:00.00 pm
   12 root      20   0     0    0    0 S  0.0  0.0   0:00.00 sync_supers
   13 root      20   0     0    0    0 S  0.0  0.0   0:00.00 bdi-default
   14 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kintegrityd/0
   15 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kblockd/0
   16 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kacpid
   17 root      20   0     0    0    0 S  0.0  0.0   0:00.01 kacpi_notify
   18 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kacpi_hotplug
   19 root      20   0     0    0    0 S  0.0  0.0   0:00.00 ata/0
   20 root      20   0     0    0    0 S  0.0  0.0   0:00.00 ata_aux
   21 root      20   0     0    0    0 S  0.0  0.0   0:00.00 ksuspend_usbd
   22 root      20   0     0    0    0 S  0.0  0.0   0:00.00 khubd
   23 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kseriod
   24 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kmmcd
   27 root      20   0     0    0    0 S  0.0  0.0   0:00.00 khungtaskd
   28 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kswapd0
   29 root      25   5     0    0    0 S  0.0  0.0   0:00.00 ksmd
   30 root      20   0     0    0    0 S  0.0  0.0   0:00.00 aio/0
   31 root      20   0     0    0    0 S  0.0  0.0   0:00.00 ecryptfs-kthrea

a volte noto che mysql utilizza 1.9 di mem, gli altri processi non passano lo 0.5


cosa può essere?