Question

I am tryiung to start a java process that requires a lot of memory. For some reason, it does not work if I specify more than 19G of RAM for the process. The free and top show that I have 23G of free memory, so I wonder why this error occurs.

           total       used       free     shared    buffers     cached
Mem:         24158       1047      23111          0         16        356
-/+ buffers/cache:        673      23485
Swap:         2204          0       2204

Starting the process with these jvm options:

-XX:+UseConcMarkSweepGC -server -d64 -Xms4g -Xmx22g

version:

java version "1.7.0_02"
Java(TM) SE Runtime Environment (build 1.7.0_02-b13)
Java HotSpot(TM) 64-Bit Server VM (build 22.0-b10, mixed mode)

However, if I specify 19G as Xmx it works.

Answer 1

The Java VM allocates memory for the heap as well as for PermGen space. Can it be that your configuration with heap space + PermGen space exceeds your free memory?

Which value is -XX:MaxPermSize set to?