//
	// Unlike (*mheap).grow, just map in everything that we
	// asked for. We're likely going to use it all.
	sysMap(unsafe.Pointer(base), userArenaChunkBytes, &gcController.heapReleased)
	sysUsed(unsafe.Pointer(base), userArenaChunkBytes, userArenaChunkBytes)

	// Model the user arena as a heap span for a large object.
	spc := makeSpanClass(0, false)
	h.initSpan(s, spanAllocHeap, spc, base, userArenaChunkPages)

	// Free extra data structures.
	sysFreeOS(unsafe.Pointer(&p.scav.index.chunks[0]), uintptr(cap(p.scav.index.chunks))*unsafe.Sizeof(atomicScavChunkData{}))

	// Subtract back out whatever we mapped for the summaries.
	// sysUsed adds to p.sysStat and memstats.mappedReady no matter what
	// (and in anger should actually be accounted for), and there's no other
	// way to figure out how much we actually mapped.