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Date: Mon, 11 Nov 1996 17:25:13 GMTServer: NCSA/1.5Content-type: text/htmlLast-modified: Wed, 06 Mar 1996 16:39:58 GMTContent-length: 2660<html><head><title>CS 537 - Quiz #5</title></head><body><table border=0 width=100% align=center><tr><td width=25%><td width=50% align=center><b>UNIVERSITY OF WISCONSIN-MADISON<br>Computer Sciences Department</b><td width=25%><tr><tr><td><b>CS 537<br>Spring 1996 </b><td><td align=right><b>Bart Miller</b><tr><td><td align=center><b>Quiz #5</b><br>Wednesday, March 6<td></table><h2>Scheduling and Synchronization</h2>For each of the following statements, indicate whether you think it isprobably true (T) or probably false (F).Then give a brief (<b>one</b> sentence) reason.There is not necessarily a single correct answer to each question, soyour one sentence explanation is the most important part of your answer.<ol><li>Small time slices always improve the average response time of a system.<table width=90% border=0 align=center><tr><td><b> Probably false:Small time slices will <i>sometimes</i> improve the average responseof the system.If the slice is too small, the context switching time will start todominate the useful computation time and everything (including responsetime) will suffer.</b></table><li>Monitors are more powerful than semaphores, because monitors automaticallyprovide mutual exclusion.<table width=90% border=0 align=center><tr><td><b>Probably false:While monitors are usually more convenient to use, they are not morepowerful.Since you can simulate semaphores with monitors, monitors are at leastas powerful as semaphores.(Of course, you know that you can also simulate monitors with semaphores,so they actually are of equal power.)</b></table><li><i>Process Control Blocks</i> (PCBs) must be stored in the operatingsystem kernel, where no process can access them.<table width=90% border=0 align=center><tr><td><b>Probably true:PCBs must be in a protected part of the memory.If users (processes) were allowed to access the PCB, they could change schedulingpriorities and perhaps access other processes' memory in an unintended manor.</b></table><li>Shortest Job First (SJF) or Shortest Completion Time First (SCTF)scheduling is difficult to build on a real operating system.<table width=90% border=0 align=center><tr><td><b>Probably true:SCTF scheduling requires knowledge of how much time a process is going totake.This requires future knowledge.You might require a user to specify the <i>maximum</i> amount of time thata process could run (and kill it if it exceeds this amount), then use avariant on SCTF.</b></table></ol><hr><H4>Last modified:Wed Mar 6 10:39:11 CST 1996by<a href="http://www.cs.wisc.edu/~bart">bart</a></b></H4></body>?? 快捷鍵說明
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