// allocated.
	//
	// Only the first 10 bits are used.
	inUse uint16

	// lastInUse indicates how many pages in this chunk were allocated
	// when we transitioned from gen-1 to gen.
	//
	// Only the first 10 bits are used.
	lastInUse uint16

	// gen is the generation counter from a scavengeIndex from the
	// last time this scavChunkData was updated.
	gen uint32