操作系统概念第六版作业解答3.pptVIP

Chapter 9 9.3 Describe the following allocation algorithms: a. First fit b. Best fit c. Worst fit First fit:有哪些信誉好的足球投注网站可用内存列表，分配第一块足够大的 Best fit:有哪些信誉好的足球投注网站整个可用内存块，分配最小足够大的 Worst fit:有哪些信誉好的足球投注网站整个可用内存块，分配最大足够大的 9-cont. 9.5 Given memory partitions of 100K, 500K, 200K, 300K, and 600K (in order), how would each of the First-fit, Best-fit, and Worst-fit algorithms place processes of 212K, 417K, 112K, and 426K (in order)? Which algorithm makes the most efficient use of memory? First fit 212 -500(288) 417 -600(183) 112 -288 426 -none Best fit 212 -300 417 -500 112 -200 426 -600 Worst fit 212 -600(388) 417 -500 112 -388 426 -none 9-cont. 9.10 Consider a paging system with the page table stored in memory. a. If a memory reference takes 200 nanoseconds, how long does a paged memory reference take? b. If we add associative registers, and 75 percent of all table references are found in the associative registers, what is the effective memory reference time? (Assume that finding a table entry in the associative registers takes zero time, if the entry is there.) a. 400, 200(page table)+200(access word) b. 250, 75%*200+25%*(200+200) 9-cont. 9.16 Consider the following segment table: What are the physical addresses for the following logical addresses? a. 0,430 b. 1,10 c. 2,500 d. 3,400 e. 4,112 a. 430600, 219+430 = 649 b. 1014, 2300+10 = 2310 c. 500100, illegal d. 400580, 1327+400 = 1727 e. 11296, illegal 9-cont. 9.18 In the IBM/370, memory protection is provided through the use of keys. A key is a 4-bit quantity. Each 2K block of memory has a key (the storage key) associated with it. The CPU also has a key (the protection key) associated with it. A store operation is allowed only if both keys are equal, or if either is zero. Which of the following memory-management schemes could be used successfully with this hardware? a. Bare machine b. Single-user system c. Multiprogramming with a fixed number of processes d. Multiprogramming with a variable number of processes e. Paging f. Segmentation a. Pro