I've noticed the last two days that the minecraft server uses a lot of memory. I tested this by fully rebooting my server. After 5 hours of uptime with 10 players online, I encountered serious issues:
after stopping the minecraft server, this happens:
Note that when the first screenshot was taken (with more than 80% mem usage) the minecraft server was totally empty, 0 players online.
I don't know if this is a known issue, if it's a java problem or minecraft related.