操作系統(tǒng)第九版部分課后作業(yè)習題答案-wenkub
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【正文】 om Belady’sanomaly from those that do not.a. LRU replacementb. FIFO replacementc. Optimal replacementd. Secondchance replacementAnswer:Rank Algorithm Suffer from Belady’s anomaly1 Optimal no2 LRU no3 Secondchance yes4 FIFO yes Discuss the hardware support required to support demand paging.Answer:For every memoryaccess operation, the page table needs to be consultedto check whether the corresponding page is resident or not and whetherthe program has read or write privileges for accessing the page. Thesechecks have to be performed in hardware. A TLB could serve as a cacheand improve the performance of the lookup operation. An operating system supports a paged virtual memory, using a centralprocessor with a cycle time of 1 microsecond. It costs an additional 1microsecond to access a page other than the current one. Pages have 1000words, and the paging device is a drum that rotates at 3000 revolutionsper minute and transfers 1 million words per second. The followingstatistical measurements were obtained from the system:? 1 percent of all instructions executed accessed a page other than thecurrent page.?Of the instructions that accessed another page, 80 percent accesseda page already in Exercises 31?When a new page was required, the replaced page was modi?ed 50percent of the time.Calculate the effective instruction time on this system, assuming that thesystem is running one process only and that the processor is idle duringdrum transfers.Answer:effective access time = (1sec + (2 sec)+ (10,000 sec + 1,000 sec)+ (10,000 sec + 1,000 sec)= ( + + + )sec= sec Consider the twodimensional array A:int A[][] = new int[100][100]。where A[0][0] is at location 200 in a paged memory system with pagesof size 200. A small process that manipulates the matrix resides in page0 (locations 0 to 199). Thus, every instruction fetch will be from page 0.For three page frames, how many page faults are generated bythe following arrayinitialization loops, using LRU replacement andassuming that page frame 1 contains the process and the other twoare initially empty?a. for (int j = 0。 i++)A[i][j] = 0。 j 100。 disk utilization 3 percentc. CPU utilization 13 percent。devices 5%Which (if any) of the following will (probably) improve CPU utilization? Explain your answer.a. Install a fasterutilization would improve. Another way toimprove performance would be to get more physical memory or a faster paging drum.a. Get a fasterCPUthus,the head is more likely to move in that direction.、Suppose that a disk drive has 5000 cylinders, numbered 0 to 4999. The drive is currently serving a request at cylinder 143, and the previous request was at cylinder 125. The queue of pending requests, in FIFO order, isb. SSTFb. The SSTF schedule is 143, 130, 86, 913, 948, 1022, 1470, 1509, 1750, 1774. The total seek distance is 1745.f. (Bonus.) The CLOOK schedule is 143, 913, 948, 1022, 1470, 1509, 1750, 1774, 86, 130. The total seek distance is 3363.12CHAPTERFileSystemImplementationPractice Exercises Consider a ?le currently consisting of 100 blocks. Assume that the ?lecontrol block (and the index block, in the case of indexed allocation)is already in memory. Calculate how many disk I/O operations arerequired for contiguous, linked, and indexed (singlelevel) allocationstrategies, if, for one block, the following conditions hold. In thec
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