java.lang.OutOfMemoryError when using joern-plot-proggraph to get cfg

[siru-yang]

I want to use joern-plot-proggraph to get cfg
On the first, it run well, but then i got java.lang.OutOfMemoryError as below

`2020-04-17 07:30:30.219+0000 INFO [API] Remote interface ready and available at [http://localhost:7474/]
Exception in thread "qtp443496729-55"
Exception: java.lang.OutOfMemoryError thrown from the UncaughtExceptionHandler in thread "qtp443496729-55"
Exception in thread "qtp443496729-57" Exception in thread "qtp443496729-56"
Exception: java.lang.OutOfMemoryError thrown from the UncaughtExceptionHandler in thread "qtp443496729-57"

Exception: java.lang.OutOfMemoryError thrown from the UncaughtExceptionHandler in thread "qtp443496729-56"
15:35:02.808 [qtp443496729-58] WARN o.e.j.util.thread.QueuedThreadPool -
java.lang.OutOfMemoryError: PermGen space
`
It seems that I can't run joern-plot-proggraph too many times.
Dose anyone know what's the problem?