As predicting the need for metadata was a complex and inconvenient exercise, the Permanent Generation was removed in Java 8 in favor of the Metaspace. From this point on, most of the miscellaneous things were moved to regular Java heap.
The class definitions, however, are now loaded into something called Metaspace. It is located in the native memory and does not interfere with the regular heap objects. By default, Metaspace size is only limited by the amount of native memory available to the Java process. This saves developers from a situation when adding just one more class to the application results in the java.lang.OutOfMemoryError: Permgen space. Notice that having such seemingly unlimited space does not ship without costs – letting the Metaspace to grow uncontrollably you can introduce heavy swapping and/or reach native allocation failures instead.
In case you still wish to protect yourself for such occasions you can limit the growth of Metaspace similar to following, limiting Metaspace size to 256 MB:
java -XX:MaxMetaspaceSize=256m com.mycompany.MyApplication