lammert - 2:38 am on Jul 14, 2010 (gmt 0)
High memory usage numbers specifically on a VPS can cause problems, because of the guaranteed vs. burst size the hoster offers. Many VPS implementations start to kill processes randomly when the amount of used memory is above the guaranteed value and the host server is getting tight on resources.
Reducing the number of idle php5-fpm processes might be the first step to try, but that can interfere with the response your visitors will get while accessing the site. You therefore have to be sure that only the number if idle waiting processes is reduced, not the number of burstable processes.
The MySQL virtual memory usage of 239MB can be tuned down if you know the size of the query results. If you only use MyISAM databases, you can switch off other database types in MySQL like the Berkeley database and InnoDB.