Methods, systems, and apparatus for determining whether an access bit is set for each page table entry of a page table based on a scan of the page table with at least one page table walker, the access bit indicating whether a page associated with the page table entry was accessed in a last scan period; incrementing a count for each page in response to determining that the access bit is set for the page table entry associated with the page; resetting the access bit after determining whether the access bit is set for each page table entry; receiving a request to access, from a main memory, a first page of data; initiating a page fault based on determining that the first page of data is not stored in the main memory; and servicing the page fault with a DMA engine.