PermGen size not expanding to fill max space available

Question

I have a java process running. With jstat I can see the the permgen utilisation and the capacity are almost identical. i.e. the current capacity is almost full but still well below the max permgensize specified.

Is this standard or should I expect to see a degree of headroom space allocated?

Standard Sun 1.5 JVM

Answer 1

permgen is something precious, so java will not allocate more than it needs to. Keep in mind that it is non-heap, so once used it will not be returned to the system until the VM dies.

So while its a good thing to have less PermGen used then MaxPermGen permits, its fine and welcome if the capacity (currently allocated) and utilisation (used part of that allocation) are close to each other.