CachePerfStats gathers performance data for single open, read and write operations as well as the whole cache entry opening. It maintains long term and short term average. The long term average filters out excessive values and it represents and average time for a given operation when the cache is not busy. The short term average represents the current cache speed. By comparing these two stats we know pretty quickly that the cache is getting slower and then we race the cache with network immediately without a delay. Otherwise the delay is based on the average cache entry open time.