See: https://www.evanjones.ca/java-bytebuffer-leak.html
This is potentially a source of lots of native memory usage.
We are clearly seeing native usage upwards to 1-4GB which doesn't make sense.
Region File usage fixed in previous patch should of tecnically only been somewhat
temporary until GC finally gets it some time later, but between all the various
plugins doing IO on various threads, this hidden detail of the JDK could be
keeping long lived large direct buffers in cache.
Set system properly at server startup if not set already to help protect from this.
Aikar