This preview shows page 1. Sign up to view the full content.
Unformatted text preview: ed with replacing the wrong virtual page is so high. Thus, operating systems use much more sophisticated replacement algorithms for DRAM caches than the hardware does for SRAM caches. (These replacement algorithms are beyond our scope.) Finally, because of the large access time of disk, DRAM caches always use write-back instead of write-through. 10.3.2 Page Tables
As with any cache, the VM system must have some way to determine if a virtual page is cached somewhere in DRAM. If so, the system must determine which physical page it is cached in. If there is a miss, the system must determine where the virtual page is stored on disk, select a victim page in physical memory, and copy the virtual page from disk to DRAM, replacing the victim page. These capabilities are provided by a combination of operating system software, address translation hardware in the MMU (memory management unit), and a data structure stored in physical memory known as a page table that maps virtual pages to physical pages. The address translation hardware reads the page table each time it converts a virtual address to...
View Full Document
- Spring '10
- The American