大連交大os第三章作業(yè)

1、精選文檔第三章作業(yè)4、Consider a swapping a system in which memory consists of the following hole sizes in memory order: 10KB, 4KB, 20KB, 18KB, 7KB, 9KB, 12KB and 15KB. Which hole is taken for successive segment requests of(a) 12KB (b) 10KB (c)9KBFor first fie? Now repeat the question for best fit, worst fit a

2、nd next fit.Solution:First fit4K9K12K15K可編輯Next fitBest fit4K 20K18K 7K15KWorst fit10K4K7K 9K 12K15K9K5、For each of the following decimal virtual addresses, compute the virtual page number and offset for a 4-KB page and for an 8-KB page: 20000, 32768, 60000.Solution:page size: 4K=4*1024=4096 20000/4

3、096=4 3616(2) 32768/4096=8 60000/4096=142656page size: 8K=8*1024=8192(1) 20000/8192=23616(2) 32768/8192=4 60000/8192=72656page number is 4, offset is 3616page number is 8, offset is 0page number is 14, offset is 2656page number is 2, offset is 3616page number is 4 offset is 0page number is 7, offset

4、 is 265622. If FIFO page replacement is used with four page frames and eight pages, how many page faults will occur with the reference string 017237103 if the four frames are initially empty? Now repeat this problem for LRU.Solution:(a) FIFO: Page fault rate=6/10=60%017232710300003333331111111007777

5、77772222222XXXXXX(b) LRU: Page fault rate=7/10=70%01723271030000333300111111111777777772222223XXXXXXx28. A computer has four page frames. The time of loading, time of last access, andthe R and M bits for each page are as shown below (the timesa re in clock ticks):PageLoadedLast ref.RM012628010123026501214027000311028511(a) Which page will NRU replace?(b) Which page will FIFO replace?(c) Which page will LRU replace?(d) Which page will s