第 8 章 主存管理 作业
答题版本 2020.12.07 20:34 试卷得分100
填空题 (18 分) 18 分 (请按题⽬中的空缺顺序依次填写答案)
(1) 205
(2) 100
(3) 300
(4) 100
(5) 185
(6) 170
(7) 205
(8) 40
(9) 185
(10) 100
(11) 300
1. Given six memory partitions of 100 MB, 170 MB,40 MB, 205 MB, 300 MB, and 185 MB (in order), how would the first-fit, best-fit, and worst-fit algorithms place processes of size 200 MB, 15 MB, 185 MB, 75 MB, 175 MB, and 80 MB (in order)?
请在下⾯空中依次填写答案。如果某进程能放⼊到空闲分区中，填写该分区的数字，如：100；如果某进程⽆法放⼊到空闲 分区中，则填写：must wait
First-fit:
a. 200M process put in ______M partition
b. 15M process put in ______M partition
c. 185M process put in ______M partition
d. 75M process put in ______M partition
e. 175M process must ______M partition
f. 80M process put in ______M partition
Best-fit
a. 200M process put in ______M partition
b. 15M process put in ______M partition
c. 185M process put in ______M partition
d. 75M process put in ______M partition
e. 175M process put in ______M partition
f. 80M process put in ______M partition
Worst-fit:
a. 200M process put in ______M partition
b. 15M process put in ______M partition
c. 185M process put in ______M partition
d. 75M process put in ______M partition
e. 175M process ______M partition
f. 80M process put in ______M partition
(12) 300
(13) 300
(14) 205
(15) 205
(16) 185
(17) must wait
(18) 170
正确答案: (1) 205 (2) 100 (3) 300 (4) 100 (5) 185 (6) 170 (7) 205 (8) 40 (9) 185 (10) 100 (11) 300 (12) 300 (13) 300 (14) 205 (15) 205 (16) 185 (17) must wait (18) 170
填空题 (18 分) 18 分 (请按题⽬中的空缺顺序依次填写答案)
(1) 3
(2) 13
(3) 41
2. Assuming a 1-KB page size, what are the page numbers and offsets for the following address references (provided as decimal numbers):
请在下⾯空中依次填写⼗进制数值答案 a. 3085 page numbers: ______ , offsets:______
b. 42095 page numbers: ______ , offsets:______
c. 215201 page numbers: ______ , offsets:______
(4) 111
(5) 210
(6) 161
正确答案: (1) 3 (2) 13 (3) 41 (4) 111 (5) 210 (6) 161
填空题 (20 分) 20 分 (请按题⽬中的空缺顺序依次填写答案)
(1) 649
(2) 2310
(3) invalid
(4) 1727
(5) invalid
正确答案: (1) 649 (2) 2310 (3) invalid (4) 1727 (5) invalid
3. Considering thesegment table, what are the physical addresses for the following logicaladdresses?
Segment Base Length 0 219 600 1 2300 14 2 90 100 3 1327 580 4 1952 96
What are the physical addresses for the following logical addresses?（Physical addresses = Segment Base Address + Offset）
请在下⾯空中依次填写⼗进制数值答案，如果是⽆效地址，请填写：invalid。 a. 0,430 Answer: ______
b. 1,10 Answer: ______
c. 2,500 Answer: ______
d. 3,400 Answer: ______
e. 4,112 Answer: ______
填空题 (16 分) 16 分 (请按题⽬中的空缺顺序依次填写答案)
(1) 1024
(2) 32
正确答案: (1) 1024 (2) 32
4. The BTV operating system has a 21-bitvirtual address, yet on certain embedded devices, it has only a 16-bit physicaladdress. It also has a 2-KB page size. How many entries are there in each ofthe following?
a. A conventional, single-level page table . Answer:______ （填写10进制数）
b. An inverted page table. Answer: ______ （填写10进制数）
填空题 (14 分) 14 分 (请按题⽬中的空缺顺序依次填写答案)
(1) 20
(2) 18
正确答案: (1) 20 (2) 18
5. Consider a logical address space of 256pages with a 4-KB page size, mapped onto a physical memory of 64 frames.
a. How many bits are required in the logical address?
b. How many bits are required in the physical address?
Answer:
a. Logical address: ______ bits b. Physical address: ______ bits
填空题 (14 分) 14 分 (请按题⽬中的空缺顺序依次填写答案)
(1) 100
(2) 64.5
正确答案: (1) 100 (2) 64.5
6. Consider a paging system with the page table stored in memory.
a. If a memory reference takes 50 nanoseconds, how long does a paged memory reference take?
b. If we add TLBs, and if 75 percent of allpage-table references are found in the TLBs, what is the effective memory reference time? (Assume that finding a page-table entry in the TLBs takes 2 nanoseconds, if the entryis present.) Answer:
a. ______ ns b. ______ ns
