PPT Slide
Translation Lookaside Buffer
- Want the cache hit ratio to be high, else paging slows down to 1/2 memory speed (recall each logical address reference takes two physical memory accesses).
- Sample calculation: if cache hit rate = 90 %, then effective memory access time:
.9 * 1 + (1-.9) * 2 = .9 +.2 = 1.1, representing a 10% slowdown over a 100% hit ratio.
- Note that TLB will require being “flushed” (all entries cleared) on a context switch, since a different page table will be in effect. This cache invalidation is typically done by OS code.