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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

(2)

(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:______

(3)

(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: ______

(4)

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

(5)

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