It's implementation is buckets divided node based hash map. Theoretically, its order is good, but not that efficient in modern hardware where the memory access is heavily cached so the data locality is more important than saving the memory copy or memory size. Using the linked list to save some memory copy doesn't benefit at all and the overhead is far greater than simply copying the contagious large chunk of memory. Especially so if the data type is trivial so the simple byte by byte memcpy is suffice.