Physical memory compaction

… Since there are several potential subsystems that could benefit from memory compaction at various granularities, the compaction subsystem was designed to track running memory compaction jobs to make sure that there are no overlaps between ongoing compactions. It exposes an interface that a consumer can use for registering a “compaction job”. A consumer registers the physical memory range it wishes to compact, a compaction function, and an optional search function. The compaction function is responsible for relocating 0-order pages within the registered physical memory range. The search function … The vm_compact subsystem does not provide implementations of compaction algorithms, search functions or data structures for compaction - all of this is left to the consumer.