Speedup max direct memory estimation via Unsafe #13650
Merged
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Motivation:
PlatformDependent::estimateMaxDirectMemory reflectevly allocates MX Beans to detect JVM's arg MaxDirectMemory (often failing to find any, because unconfigured).
Modifications:
Allow unsafe to find Bits's max memory static field and use it as a fast path to detect the same direct memory limits used by the JVM runtime
Result:
Faster and less memory hungry (in term of mallocs) startup
Porting of #13643