v11stanford.edu-Thrashing_and_Working_Sets

v11stanford.edu-Thrashing_and_Working_Sets - Thrashing and...

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http://w w w .stanford.edu/~ouster/cgi-bin/cs140-w inter12/lecture.php?topic=thrashing January 11, 2012 Thrashing and Working Sets Thrashing and Working Sets Lecture Notes for CS 140 Winter 2012 John Ousterhout Readings for this topic from Operating System Concepts : Sections 9.6, 9.10. Normally, if a thread takes a page fault and must wait for the page to be read from disk, the operating system runs a different thread while the I/O is occurring. Thus page faults are "free"? What happens if memory gets overcommitted? Suppose the pages being actively used by the current threads don't all fit in physical memory. Each page fault causes one of the active pages to be moved to disk, so another page fault will occur soon. The system will spend all its time reading and writing pages, and won't get much work done. This situation is called thrashing ; it was a serious problem in early demand paging systems. How to deal with thrashing?
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This note was uploaded on 04/02/2012 for the course CS 140 taught by Professor Rosenblum during the Winter '08 term at Stanford.

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v11stanford.edu-Thrashing_and_Working_Sets - Thrashing and...

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