How is LRU not simple? The page replacement policy in Linux is simple it's just makes use of available information - The algorithm does not make the system. Clock-pro is not in Linux and I doubt it ever will be. The goal in creating manageable code is passing the information that you know to the next person that doesn't by using comments and even Linux doesn't do this at all so hack-ability of any non trivial parts is near impossible without a few months of poking.