Getting Perm Gen space issue in running elasticsearch cluster
The best solution is to use a "Java 8" JVM.
While you could modify the amount of heap your Java 7 JVM is using (by setting -XX:MaxPermSize=... if you are using an Oracle JVM), if you just upgrade the JVM to version 8, then you don't even need to tune the permgen size.
This is because in JVM 8, the permgen size shares the heap in a non-partitioned way, meaning that you will only run out of permgen space when you run out of heap.