interpreting top

[Doug]

Hello:

I work on a big machine at work.  Here is the command top:


top - 15:36:46 up 80 days,  3:14,  4 users,  load average: 0.00, 0.00, 0.00
Tasks:  89 total,   2 running,  87 sleeping,   0 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
Mem:  16440256k total, 16280920k used,   159336k free,    67484k buffers
Swap:  7807580k total,    83564k used,  7724016k free, 15646216k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
    1 root      15   0  5076  152   68 S    0  0.0   0:02.49 init
    2 root      RT   0     0    0    0 S    0  0.0   0:00.01 migration/0
    3 root      34  19     0    0    0 S    0  0.0   0:00.66 ksoftirqd/0
    4 root      RT   0     0    0    0 S    0  0.0   0:00.00 watchdog/0
    5 root      RT   0     0    0    0 S    0  0.0   0:00.02 migration/1

Lots of sleeping is happening.  Nothing has been going on for a while
(load average: 0.00, 0.00, 0.00)  One thing I found curious is the
line started Mem: there still is a large value under used.  I can see
that some swap was used (when, I do not know).  I guess the rational
explanation is that nearly all of this is cache memory.  I guess linux
as an OS is passive about tossing this stuff away.  It is hard to take
the Mem: line as a warning marker if it remains so high when times are
calm.  Can I/should I do anything?

Doug