[理工] OS time-sharing 恐龍原文描述的問題

[TMDTMD2487 (ㄚ冰)]

如果你手邊有書的話 9/e page.20 最下面

In a time-sharing system, the OS must ensure reasonable
response time. This goal is sometimes accomplished through
swapping, whereby processes are swapped in and out of main
memory to the disk.

A more common method for ensuring reasonable response time
is virtual memory,a technique that allows the execution of
a process that is not completely in memory. The main
advantage of the virtual-memory scheme is that it enables
users to run programs that are larger than actual physical
memory. Futher, it abstracts main memory into a large,
uniform array of storage, separating logical memory as
view by the user from physical memory.


我記得之前有一題多選題 有一個選項抄這邊前兩三行的

不過他把 response time 改成 turnaround time

結果我還想說是因為swap不能改善時間 然後就看到這段話

所以說為什麼swap或是virtual memory可以改善response??

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※ 編輯: TMDTMD2487 (134.208.0.169), 11/10/2017 21:42:51
※ 編輯: TMDTMD2487 (134.208.0.169), 11/10/2017 21:43:21
推 leoone: 我想是因為 Time sharing 要求極短暫的response time 才
→ leoone: 能在不同使用者之間切換，當使用者在執行程式時只要放部
→ leoone: 分程式在MEM中，以縮短search 跟 compare time ，就算被sw
→ leoone: ap到Disk時間很長，反正是IO 切到其他process跑就好了
推 can18: 我認為是 若是需要整個swap in&out 需要很久
→ can18: 但virtual memory容許部分載入 就可以恢復執行 會快的多
→ can18: 就response time 而言
→ can18: 抱歉搞錯原po問題
→ can18: 若不用swap或virtual mem，當memory space不足時 user 就
→ can18: 必須等別人的process跑完才可以換他的，這就不是reasonable
→ can18: response time
謝兩位大概知道為什麼了！
※ 編輯: TMDTMD2487 (114.136.168.188), 11/11/2017 08:20:56