大连交大os第三章作业(共2页).doc
精选优质文档-倾情为你奉上第三章作业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 and next fit.Solution:First fit10K4K20K18K7K9K12K15K12K10K9KNext fit10K4K20K18K7K9K12K15K12K10K9KBest fit10K4K20K18K7K9K12K15K12K10K9KWorst fit10K4K20K18K7K9K12K15K12K10K9K 5、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(1) 20000/4096=43616 page number is 4, offset is 3616(2) 32768/4096=8 page number is 8, offset is 0(3) 60000/4096=142656 page number is 14, offset is 2656page size: 8K=8*1024=8192(1) 20000/8192=23616 page number is 2, offset is 3616(2) 32768/8192=4 page number is 4 offset is 0(3) 60000/8192=72656 page number is 7, offset 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 if the four frames are initially empty? Now repeat this problem for LRU.Solution:(a) FIFO: Page fault rate=6/10=60%01723271030000333333111111100777777772222222××××××(b) LRU: Page fault rate=7/10=70%01723271030000333300111111111777777772222223×××××××28. A computer has four page frames. The time of loading, time of last access, and the 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 second chance replace?Solution:(a) Page 2 (2) (b) Page 3 (3) (c) Page 1 (1) (d) Page 2 (2)专心-专注-专业
