[理工] [OS]幾題問題

作者crazyjoe (梨子)

看板Grad-ProbAsk

標題[理工] [OS]幾題問題

時間Wed Feb 24 22:46:33 2010

1.Which of the following technologies are not designed to overcome the low efficiendy incurred by large page table sizes. (A)limit regester (B)TLB 答案為A，請問TLB為什麼可以? 2.Which of the following statements is false?(台大電機97) (B)System calls are executed with privileged instructions which are not supposed to be use by user programs. (D)In practices,the SJF scheduling algorithm may not be optimal in average waiting time. 3.Which of the schedules results in the minimal average waiting time(over all processes)?(台大電機98) (A)FCFS (B)SJF (C)Nonpreemptive Priority (D)RR -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 140.116.243.66

推 polomoss:3.B 02/24 22:47

→ taitin:TLB就是pt的快取，速度比pt快 02/24 22:52

→ taitin:2 D 02/24 22:53

推 willow02:system call 執行的都是privileged instructions嗎? 02/24 23:16

→ taitin:對 02/24 23:21

→ taitin:行程管理，檔案管理，裝置管哩，資訊維護，通訊，保護 02/24 23:22

推 willow02:system call 是指要求OS提供服務 OS轉到kernel mode 02/25 00:04

→ willow02:再去執行service function function中通常會用到 02/25 00:05

→ willow02:privileged instruction 但並非全部是privileged inst 02/25 00:06

→ willow02:是這樣說的嗎? 02/25 00:06

推 stevenwin:1應該是B，計組版本的解決方法有limit register 02/25 00:11

→ taitin:我覺得所有privilege都透過SYS CALL 02/25 00:14

推 trovadores:2.(B)是false system call是給user call的 02/25 00:16

→ trovadores:不可能為priviliged 洪逸洪捷解答書說的 02/25 00:17

→ trovadores:但是字面上看起來我覺得是對的= = 02/25 00:18

→ taitin:我發現我第二題看錯，false的是B 02/25 00:20

→ taitin:不是...是D...又看錯請忽略上一樓 02/25 00:21

推 willow02:我怎麼覺得洪逸的翻譯怪怪的阿XD 是不是解讀錯了? 02/25 00:21

→ taitin:信洪逸的話......就.... 02/25 00:22

→ willow02:第2題是單選嗎? 02/25 00:22

→ taitin:我覺得B對阿 02/25 00:23

推 hoverg:我也覺得b對耶… 02/25 00:44

→ crazyjoe:第一題他問的是可以改善SIZE大小 TLB 怎麼改善的...? 02/25 12:00

→ crazyjoe:第二題D對的話又跟第三題矛盾... 可是又覺得B怪怪的QQ 02/25 12:01

推 dadan:第一題的意思叫做"PageTable太大造成的「效率」低落" 02/26 01:00

→ dadan:解法就是造個TLB來當page table的cache 這是TLB存在的意義啊 02/26 01:00