[理工] [os] 94清大

看板Grad-ProbAsk作者compulsory (まけない!)時間15年前 (2011/01/07 19:25)推噓2(2推 0噓 6→)

留言8則, 2人參與討論串1/1

A computer whose processes have 1024 pages in their address spaces keeps it's page tables in memory. The overhead reading aword from the page table is 500ns . In order to reduce the overhead, the computer has a TLB, which holds 32 (virtual page,physical page frame)pairs, and can do a look up in 100ns. What hit rate is needed to reduce the mean overhead to 200ns? 個人的想法是: 設P為TLB的hit rate 如果TLB hit 存取時間100+500=600ns 如果TLB miss 存取TLB的時間加上存取一次page table加上一次memory的時間 100+500+500=1100ns P*600+(1-P)*1100=200 可是參考書的答案是 P*100+(1-P)*600=200 我哪裡想錯了?? -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 122.116.13.191

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compulsory

01/07 19:32, , 1^F

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christianSK

01/07 19:32, , 2^F

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christianSK

01/07 19:33, , 3^F

01/07 19:33, 3^F