During a cache miss, some other previously existing cache entry is removed in order to make room for the newly retrieved data. The heuristic used to select the entry to replace is known as the replacement policy. One popular replacement policy, "least recently used" (LRU), replaces the oldest entry, the entry that was accessed less recently than any other entry (see cache algorithm). More efficient caching algorithms compute the use-hit frequency against the size of the stored contents, as well as the latencies and throughputs for both the cache and the backing store. This works well for larger amounts of data, longer latencies, and slower throughputs, such as that experienced with hard drives and networks, but is not efficient for use within a CPU cache.