I've 3GB RAM on my (hosting) server.
When I last checked with 'free', I realised that it had some KB of swap
used, while having >2GB of RAM unused:
[root@ns1 mail]# free
total used free shared buffers cached
Mem: 3115152 969056 2146096 0 163456 303584
-/+ buffers/cache: 502016 2613136
Swap: 1052152 8 1052144
I assume that there has been a peak in usage.
How do I check what app/site sucked the RAM?