《Operating System Concepts》学习第 34 天，p408-p448 总结，总计 41 页。

一、技术总结

2.page-replacement algorithm

In memory management, the algorithm that chooses which victim frame of physical memory will be replaced by a needed new frame of data.

(1)FIFO pagte replacement

(2)optimal page replacement

(3)LRU page replacement

(4)LRU-Approxiation page replacement

(5)Counting-Base page replacement

2.thrashing

Paging memory at a high rate. A system thrashes when there is insufficient physical memory to meet virtual memory demand。

二、英语总结(生词：3)

1.approximation

(1)approximate: ad-("to") + proximus("nearest")

vi/vt. to be almost the same as. adj. not completely accurate but close(大概的).

(2)approximation: noun of action from approximate

c. a value that is nearly but not exactly correct.

(3)示例

Could you give me a rough approximation of how many people will be coming?

2.expansion

(1)expand: ex-("out") + pandere("to spread, stretch")

vi/vt. to increase in size, number or importance(扩大，增加)。

(2)expansion

c/u. the increase in size, number or importance(扩大，增加)。

(3)示例

An expansion of this idea is to maintain a list of modified pages(《Operating System Concepts》第 412 页)。

3.reaper

(1)reap

vi/vt. to cut and collect a grain crop(收割)。

(2)reaper

c. a machine that cut and collect crops(收割机)。

(3)示例

Such kernel routines are often known as reapers, and they may apply any of the page-replacement algorithms covered in Section 10.4(《Operating System Concepts》第 417 页)。

关于英语的注解同步更新汇总到 https://github.com/codists/English-In-CS-Books 仓库。

三、其它

第 10 章(Virtual Memory)简评：介绍虚拟内存相关的 demand paging, page-fault, page-replacement algorithm, 感觉真抽象啊。

四、参考资料

1. 编程

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

2. 英语

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

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

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