4. (8 points) Assume that we have a computer that uses virtual memory. It has a

Question

4. (8 points) Assume that we have a computer that uses virtual memory. It has a TLB, a cache, and a page table. Furthermore, we can assume the following: · A TLB hit requires 5 ns A cache hit requires 12 ns A memory reference requires 25 ns .A disk reference requires 200 ms (this includes updating the page table, cache, and TLB) The TLB hit ratio is 90% The cache hit rate is 98% The page fault rate is .001% .On a page fault, the page is fetched from disk, and access is restarted. In other words, you must re-do the access after the disk block is retrieved (see Slide 57 in Chapter 6) All references are sequential (no overlap, nothing done in parallel) For each of the following, provide the total time taken for the access. Again, you may want to use the logic of Slide 57 as a guide. a. TLB hit, cache hit b. TLB miss, page table hit, cache hit c. TLB miss, page table hit, cache miss d. TLB miss, page table miss

Explanation / Answer

TLB_hit_time := TLB_search_time + memory_access_time

TLB_miss_time := TLB_search_time + memory_access_time + memory_access_time

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