Off heap

[LinHu2016]

Introduce Off-Heap Technology for Large Arrays in Balanced Region-Based Garbage Collector carryforward from https://github.com/eclipse-openj9/openj9/pull/14667

[dmitripivkine]

There is summary across platforms for case decommit does nothing (memory is not disclaimed). So, because of incompatibility with off-heap we either should not allow this modes or disallow off-heap (TBD).

AIX:

• memory allocated in 16m or 16g pages (supports 4k and 64k pages)

ZOS:

• memory allocated in any fixed (non-pageable) pages (supports 4k pageable and 1m pageable, does not support 1m fixed and 2g fixed)

Linux:

• memory allocated in Large Shared pages (supports small pages and Transparent Huge Pages, does not support non-transparent Huge pages)

OSX:

• no limitations

Windows:

• memory allocated in any pager other than 4k (2m pages)

ZTPF:

• does not allow to recommit any memory

[dmitripivkine]

On the top of this, disclaiming memory can be disabled by -XX:-DisclaimVirtualMemory for all platforms.