+ s.userArenaChunkFree = makeAddrRange(base, base+s.elemsize)
+
+ // Put the large span in the mcentral swept list so that it's
+ // visible to the background sweeper.
+ h.central[spc].mcentral.fullSwept(h.sweepgen).push(s)
+
+ if goexperiment.AllocHeaders {
+ // Set up an allocation header. Avoid write barriers here because this type
+ // is not a real type, and it exists in an invalid location.
+ *(*uintptr)(unsafe.Pointer(&s.largeType)) = uintptr(unsafe.Pointer(s.limit))
+ *(*uintptr)(unsafe.Pointer(&s.largeType.GCData)) = s.limit + unsafe.Sizeof(_type{})
+ s.largeType.PtrBytes = 0
+ s.largeType.Size_ = s.elemsize
+ }