If a particular core instance doesn't use up too much memory, then we don't charge the host OS for that memory.
The strange thing here is that, testing locally on Windows 10, we were already getting the desired semantics even with SEC_COMMIT and not SEC_RESERVE. This commit is still important because:
1) Windows might be providing me an optimization it can't guarantee,
2) Linux might not be able to provide the same optimization
3) In any event, this patch also trims down xor snapshots to match the actual needed size.
The refactoring of platform abstractions should never have changed the name of the public interface. No one cares about MemoryBlockWindows or MemoryBlockUnix - those names are impl details.
nattthebear