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The foreign memory API which is currently incubating should help with most of these limitations: https://openjdk.java.net/jeps/419 https://openjdk.java.net/jeps

• native_samples 5y ago
  Right - specifically they invented a way to make closing an mmapped segment safe and fast. The reason you can't officially (without private APIs) unmap something in current Java is because if you did then other threads would segfault, and "no segfaults" is kind a defining characteristic of Java. The new API fixes this using more VM magic, so closing a mapping from one thread will cause other threads to throw exceptions, but this is done without sacrificing performance (it doesn't require checking a status every time you read from memory).