operating system concepts

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1、Sept29,2000•Processesandconcurrentprogramming–Processes–Processprimitives–SynchronizationandcommunicationOperatingSystemConcepts1.1CS134a,2000SilberschatzandGalvin1999Whatisaprocess?•An“activityresultingresultingfromtheexecutionofaprogram,withdata,byaprocessor.’’•C

2、onceptually,eachprocesshasitsown:–Processor–Programstoredinmemory–Programstate:registers,memory,PC,environment,…(whatelse?)OperatingSystemConcepts1.2CS134a,2000SilberschatzandGalvin1999Processmodel•TheOSisacollectionofconcurrentprocesses•Processesoperatealmostindep

3、endentlyofoneanother•Processescooperatewithmessagesandsignals•Processescompeteforresources•Thekernel“virtualizes”theCPU(providestheillusionthateachprocesshasitsownCPU)•Whataboutmultiple-CPUmachines?OperatingSystemConcepts1.3CS134a,2000SilberschatzandGalvin1999Whypr

4、ocesses?•Alogicalconstructiontocopewithcomplexity•Componentsinacomplexsystemmusthave–Well-definedfunctionality–Well-definedinterfaces•Operatingsystemsarereactivesystems–Thesystemreactstoevents(timers,I/O,faults,etc)–Eventsoccuratunpredictabletimesandwithvaryingfrequ

5、encyOperatingSystemConcepts1.4CS134a,2000SilberschatzandGalvin1999ProcessflowgraphsSequentialParallelCombinationGeneralOperatingSystemConcepts1.5CS134a,2000SilberschatzandGalvin1999Exampleprocessflowa*b+c/dr1=a*br2=c/dr1+r2OperatingSystemConcepts1.6CS134a,2000Silb

6、erschatzandGalvin1999Language•Sequentialexecution:(P1;P2)•Parallelexecution:cobeginP1

7、P2

8、…

9、Pncoend•Example:cobeginr1=a*b

10、r2=c/dcoend;r3=r1+r2OperatingSystemConcepts1.7CS134a,2000SilberschatzandGalvin1999Fork/Join•Instructionsarelabeled•forkl:startsanewprocessatloc

11、ationl•joinm,l:decrementsm,jumptolifm=0•quit:terminatesprocessOperatingSystemConcepts1.8CS134a,2000SilberschatzandGalvin1999Example:imageprocessing•Applykernelto(nxn)bitmap/*Forkn^2processes*/intm=n*n;privateinti,j;for(i=0;i!=n;i++){for(j=0;j!=n;j++)forke;};/*Compu

12、teapixelandterminate*/e:image[i][j]=kernel(image,i,j);joinm,r;quit;r:OperatingSystemConcepts1.9CS134a,2000SilberschatzandGalvin1999Unix•f