大连交大os第三章作业.docxVIP

4K7K9K12K15K10K4K7K12K15K4K20K18K7K15K10K4K7K9K12K 4K 7K 9K 12K 15K 10K 4K 7K 12K 15K 4K 20K 18K 7K 15K 10K 4K 7K 9K 12K 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)9KB For first fie? Now repeat the question for best fit, worst fit and next fit. Solution: First fit 10K 10K  20K 12K  18K 9K Next fit 20K 12K  18K 10K  9K 9K Best fit 10K 10K  9K 9K  12K 12K Worst fit 20K 12K  18K 10K  15K 9K 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 20000/4096=4…3616 page number is 4, offset is 3616 32768/4096=8 page number is 8, offset is 0 60000/4096=14…2656 page number is 14, offset is 2656 page size: 8K=8*1024=8192 20000/8192=2…3616 page number is 2, offset is 3616 32768/8192=4 page number is 4 offset is 0 60000/8192=7…2656 page number is 7, offset is 2656 22. 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% 0 1 7 2 3 2 7 1 0 3 0 0 0 0 3 3 3 3 3 3 1 1 1 1 1 1 1 0 0 7 7 7 7 7 7 7 7 2 2 2 2 2 2 2 × × × × × × (b) LRU: Page fault rate=7/10=70% 0 1 7 2 3 2 7 1 0 3 0 0 0 0 3 3 3 3 0 0 1 1 1 1 1 1 1 1 1 7 7 7 7 7 7 7 7 2 2 2 2 2 2 3 × × × × × × × 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): Page Loaded Last ref. R M 0 126 280 1 0 1 230 265 0 1 2 140 270 0 0 3 110 285 1 1 Which page will NRU replace? Which page will FIFO replace? Which page will LRU replace? Which page will second chance replace? Solution: (a) Page 2 (2) (b) P