1. A method of tracking page characteristics in a memory system, the method comprising: storing a plurality of pages in a memory; determining a first number of pages in the plurality of pages stored in memory that are not be swapped out to a hard-disk drive; reading the plurality of pages from the memory, and while reading the plurality of pages from the memory; updating the page characteristic for a second number of pages in the plurality of pages stored in the memory; and not updating the page characteristic for the first number of pages.