Using 4KB page size for virtual memory is obsolete

A 4KB page size has been used for Virtual Memory since the sixties. In fact, today, the most common page size is still 4KB. Choosing a page size is finding the middle ground between several factors. On the one hand, a smaller page will reduce fragmentation; thus saving memory space. On the other hand, a larger page will increase TLB coverage; thus eliminating the need to access memory resident page tables. During the years that the 4KB page has been employed, memory size has increased from Megabytes to Gigabytes. We can sacrifice some space for higher performance. With the aim of obtaining the optimal page size, we simulated applications from the SPEC2000 suite. We measured TLB misses and memory usage of all page sizes that are powers of two, ranging from 4KB to 256KB. Based on our results, we show that the use of 16KB size for the base page is the recommended selection. Another way of increasing page size and TLB coverage is using superpages. Many machines support several page sizes, which let the OS use several page sizes. In this paper we survey various ways of making the most of superpages. We adopt a simple solution of superpaging with two page sizes. Based on our results, we suggest a base page of 16KB for code or small data segments and a larger page of 256KB for large data segments.