if l2 == nil {
				throw("out of memory allocating heap arena map")
			}
			if h.arenasHugePages {
				sysHugePage(unsafe.Pointer(l2), unsafe.Sizeof(*l2))
			} else {
				sysNoHugePage(unsafe.Pointer(l2), unsafe.Sizeof(*l2))
			}
			atomic.StorepNoWB(unsafe.Pointer(&h.arenas[ri.l1()]), unsafe.Pointer(l2))
		}

		if l2[ri.l2()] != nil {
			throw("arena already initialized")
		}