A new page table for 64-bit address spaces

Most computer architectures are moving to 64-bit virtual address spaces. We first discuss how this change impacts conventional linear, forward-mapped, and hashed page tables. We then introduce a new page table data structure-clustered page table-that can be viewed as a hashed page table augmented with subblocking. Specifically, it associates mapping information for several pages (e.g., sixteen) with a single virtual tag and next pointer. Simulation results with several workloads show that clustered page tables use less memory than alternatives without adversely affecting page table access time. Since physical address space use is also increasing, computer architects are using new techniques-such as superpages, complete-subblocking, and partial-subblocking-to increase the memory mapped by a translation lookaside buffer (TLB). Since these techniques are completely ineffective without page table support, we next look at extending conventional and clustered page tables to support them. Simulation results show clustered page tables support medium-sized superpage and subblock TLBs especially well.