《Operating System Concepts》學習第 23 天，p203-p207 總結，總計 5 頁。

一、技術總結

1.vmstat

Linux 系統上 vmstat 命令的作用是“Report virtual memory statistics”。

2.scheduling algorithms

(1)FCFS(first-come first-serve)

(2)SJF(shortest-job-first)

準確的叫法應該是“shortest-next-CPU-burst”。

二、英語總結(生詞：4)

1.convoy

(1)convoy: con-("together") + via("road")

c. a group of vehicles traveling together(車隊，船隊等)。

vt. accompany (a group of vehicles) for protection(護送)。

(2)示例

There is a convoy effect as all the other processes wait for the one big process to get off the CPU(《Operating System Concepts》第 207 頁)。

以下是個人的理解：其它所有進程(all the other processes)排在一個重量級的進程(one big process后等待，這種場景很像“護送，護航”，所以稱為“convoy effect”，effect的意思是"a result or consequence of an action "。convoy effect 直譯就是“護航效應”、“護送效應”。

2.disastrous

(1)disaster: dis-("ill") + astro("star, planet")

c/u. great harm。

(2)disastrous: adjective form of disaster。

adj. extremely bad。

示例：It would be disastrous to allow one process to keep the CPU for an extended period(《Operating System Concepts》第 207 頁)。

3.provable

(1)prove: *per-("forward") + *buh("to be")

vt. to show sth is true。

(2)provable:

adj. be able to be proven。

(3)probably:

adv. in a way that be able to be proven。

示例：The SJF scheduling algorithm is provably optimal, in that it gives the minimum average waiting time for a given set of processes(《Operating System Concepts》第 207 頁)。

4.optimal & optimum

(1)optimal: optimum + -al

adj. best。

(2)optimal vs optimum

optimum也可以做形容詞，意思和 optimal 一樣，意為"best"。看到一種說法是“In some areas of mathematics, an optimal value is essentially a local optimum; i.e. it's an optimum value in its neighborhood.”。這里記錄一些用例，方便后續(xù)比較，理解。

The SJF scheduling algorithm is provably optimal, in that it gives the minimum average waiting time for a given set of processes(《Operating System Concepts》第 207 頁)。

關于英語的注解同步更新匯總到 https://github.com/codists/English-In-CS-Books 倉庫。

三、其它

今天沒有什么想說的。

四、參考資料

1. 編程

(1) Abraham Silberschatz，Peter Baer Galvin，Greg Gagne《Operating System Concepts》：https://book.douban.com/subject/30272539/

2. 英語

(1) Etymology Dictionary：https://www.etymonline.com

(2) Cambridge Dictionary：https://dictionary.cambridge.org

歡迎搜索及關注：編程人(a_codists)