1、ACPUschedulingalgorithmdeterminesanorderfortheexecutionofitsscheduledprocesses.Givennprocessestobescheduledononeprocessor,howmanypossibledifferentschedulesarethere?Giveaformulaintermsofn.答：共有n！=n*(n-1)*(n-2)*1種不同樣度方法。2.Definethedifferencebetweenpreemptiveandnonpreemptivescheduling.Statewhystrictnonp

2、reemptiveschedulingisunlikelytobeusedinacomputercenter.答：非占式度：一旦CPU被分配一個程，那么程會素來使用CPU直到程止或切到等待狀主放CPU?？烧际蕉龋寒?dāng)一個程在CPU上運行，程序的CPU使用可以被另一個新程剝，被占的程序的狀被保存在PCB中，并入就列，等待下一次運行。若是一個系采用的是非可占式度，并采用先度，那么先比低的程可能永都在等待被行，造成。種情況就需要采用老化技來防范。因此一個算機(jī)中心最好不要采用格的非占式度。Considerthefollowingsetofprocesses,withthelengthoftheCPU-b

3、ursttimegiveninmilliseconds:TheprocessesareassumedtohavearrivedintheorderP1,P2,P3,P4,P5,allattime0.a.DrawfourGanttchartsillustratingtheexecutionoftheseprocessesusingFCFS,SJF,anonpreemptivepriority(asmallerprioritynumberimpliesahigherpriority),andRR(quantum=1)scheduling.b.Whatistheturnaroundtimeofeac

4、hprocessforeachoftheschedulingalgorithmsinparta?c.Whatisthewaitingtimeofeachprocessforeachoftheschedulingalgorithmsinparta?d.Whichoftheschedulesinpartaresultsintheminimalaveragewaitingtime(overallprocesses)?FCFSP1P2P3P4P501011131419答：a）非搶占式SJFP2P4P3P5P10124919非搶占式優(yōu)先級P2P5P1P3P4016161819RR（時間片=1）P1P2P

5、3P4P5P1P3P5P1P5P1P5P1P5P1P1P1P1P1012345678910111213141516171819）周轉(zhuǎn)時間：FCFS：P1=10；P2=11；P3=13；P4=14；P5=19；SJF：P1=19；P2=1；P3=4；P4=2；P5=9；非搶占式優(yōu)先級：P1=16；P2=1；P3=18；P4=19；P5=6；RR：P1=19；P2=2；P3=7；P4=4；P5=14；c）等待時間：FCFS：P1=0；P2=10；P3=11；P4=13；P5=14；SJF：P1=9；P2=0；P3=2；P4=1；P5=4；非搶占式優(yōu)先級：P1=6；P2=0；P3=16；P4=18；

6、P5=1；RR：P1=9；P2=1；P3=5；P4=3；P5=9；d）平均等待時間：FCFS：(0+10+11+13+14)/5=9.6SJF：(9+0+2+1+4)/5=3.2非搶占式優(yōu)先級：(6+0+16+18+1)/4=10.25RR：(9+1+5+3+9)/4=6.75因此，SJF算法的平均等待時間最少。Supposethatthefollowingprocessesarriveforexecutionatthetimesindicated.Eachprocesswillrunthelistedamountoftime.Inansweringthequestions,usenonpre

7、emptiveschedulingandbasealldecisionsontheinformationyouhaveatthetimethedecisionmustbemade.a.WhatistheaverageturnaroundtimefortheseprocesseswiththeFCFSschedulingalgorithm?b.WhatistheaverageturnaroundtimefortheseprocesseswiththeSJFschedulingalgorithm?c.TheSJFalgorithmissupposedtoimproveperformance,but

8、noticethatwechosetorunprocessP1attime0becausewedidnotknowthattwoshorterprocesseswouldarrivesoon.ComputewhattheaverageturnaroundtimewillbeiftheCPUisleftidleforthefirst1unitandthenSJFschedulingisused.RememberthatprocessesP1andP2arewaitingduringthisidletime,sotheirwaitingtimemayincrease.Thisalgorithmcouldbeknownasfuture-knowledgescheduling.答：a)執(zhí)行序次為：P1，P2，P3；平均