推 f31816:因為那是去TLB找所花之時間 去找了才知有沒有在TLB中 05/15 02:20
→ f31816:沒找到會要再多花500ns去page table找 05/15 02:20
→ f31816:我們無法事先預知在TLB中會找到否 所以找到機率與其無關 05/15 02:21
→ f31816:必定要在TLB找一次 05/15 02:22
→ bernachom:點醒我了，大概是我太久沒唸了...謝謝您 05/15 02:33
想確認一下..是不是我搞錯了..
題目是:
A computer whose processes have 1024 pages in their address
spaces keeps its page tables in memory. The overhead required for
reading a word from the page table is 500 nsec. 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 100 nsec.
What hit rate is needed to reduce the mean overhead to 200 nesec?
書上寫: 假設TLB的hit rate 為h，則:
100ns+(1-h)*500ns=200ns
h=80%
我的問題是，那為什麼100ns不需要乘上h呢?
謝謝幫忙
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 61.228.100.113