Virtual memory uses a page table to keep track of the mapping of virtual address to physical address. In this example, assume 4KiB pages, a 4-entry fully associative TLB and a LRU (least recently used) replacement algorithm. The status of the TLB and Page table are shown below TLB Valid Dirty Ref Tag Physical Page Number 1 0 0 11 12 1 1 1 3 6 1 0 0 5 11 1 0 1 4 9 Page table Valid Physical Address or Disk GREENHO 0 1 5 0 Disk 0 Disk 1 6 1 9 5 1 11 6 0 Disk 7 1 4 B 0 Disk 9 0 Disk 10 1 3 11 1 12 Example. Let us assume that the CPU sends the following virtual 4669. We need to figure out the virtual page number. Since we are using decimal numbers, it is necessary to perform arithmetic operations virtual page number = [virtual address page size 146691 4096 = 1 This page is NOT in TLB (we check the tags). We check in entry 1 of the page table, this is a not valid entry (0); this page is NOT in main memory, TLB miss. Thus, we have a page fault. We need to include the page in page table and TLB. TLB Valid Dirty Ref Tag Physical Page Number 1 0 0 11 1 1 1 3 S 6 1 0 1 1 7 1 0 1 4 9 Since TLB is fully associative we can place the new entry in any place. In addition there is a not valid entry that can be used. The physical page is provided by the OS. We can use an address that is not in use; such as 1, 2, 7, let us use 7 Page table Valid Physical Address or Disk 10 OHNM 600 9 1 5 1 7 0 Disk 1 6 1 9 5 1 11 0 Disk 1 4 B 0 Disk 9 0 Disk 1 3 11 1 8 Let us assume that now the CPU send the following virtual addresses. (Please update TLB and Page table if needed.) a) 2227 TLB Valid Dirty Ref Tag Page table Physical Address Valid Physical Page Number or Disk 0 1 5 1 0 0 11 8 1 1 1 3 I 0 1 1 0 1 314 6 7 9 12345 do 1 7 0 Disk 1 6 1 1 11 6 0 Disk 7 1 4 8 0 Disk 9 о Disk 10 1 3 11 1 b) 13916 followed by c) 34586 (Initial TLB and Page table status comes from what happen in (a))
Virtual memory uses a page table to keep track of the mapping of virtual address to physical address. In this example, assume 4KiB pages, a 4-entry fully associative TLB and a LRU (least recently used) replacement algorithm. The status of the TLB and Page table are shown below TLB Valid Dirty Ref Tag Physical Page Number 1 0 0 11 12 1 1 1 3 6 1 0 0 5 11 1 0 1 4 9 Page table Valid Physical Address or Disk GREENHO 0 1 5 0 Disk 0 Disk 1 6 1 9 5 1 11 6 0 Disk 7 1 4 B 0 Disk 9 0 Disk 10 1 3 11 1 12 Example. Let us assume that the CPU sends the following virtual 4669. We need to figure out the virtual page number. Since we are using decimal numbers, it is necessary to perform arithmetic operations virtual page number = [virtual address page size 146691 4096 = 1 This page is NOT in TLB (we check the tags). We check in entry 1 of the page table, this is a not valid entry (0); this page is NOT in main memory, TLB miss. Thus, we have a page fault. We need to include the page in page table and TLB. TLB Valid Dirty Ref Tag Physical Page Number 1 0 0 11 1 1 1 3 S 6 1 0 1 1 7 1 0 1 4 9 Since TLB is fully associative we can place the new entry in any place. In addition there is a not valid entry that can be used. The physical page is provided by the OS. We can use an address that is not in use; such as 1, 2, 7, let us use 7 Page table Valid Physical Address or Disk 10 OHNM 600 9 1 5 1 7 0 Disk 1 6 1 9 5 1 11 0 Disk 1 4 B 0 Disk 9 0 Disk 1 3 11 1 8 Let us assume that now the CPU send the following virtual addresses. (Please update TLB and Page table if needed.) a) 2227 TLB Valid Dirty Ref Tag Page table Physical Address Valid Physical Page Number or Disk 0 1 5 1 0 0 11 8 1 1 1 3 I 0 1 1 0 1 314 6 7 9 12345 do 1 7 0 Disk 1 6 1 1 11 6 0 Disk 7 1 4 8 0 Disk 9 о Disk 10 1 3 11 1 b) 13916 followed by c) 34586 (Initial TLB and Page table status comes from what happen in (a))
Computer Networking: A Top-Down Approach (7th Edition)
7th Edition
ISBN:9780133594140
Author:James Kurose, Keith Ross
Publisher:James Kurose, Keith Ross
Chapter1: Computer Networks And The Internet
Section: Chapter Questions
Problem R1RQ: What is the difference between a host and an end system? List several different types of end...
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Transcribed Image Text:Virtual memory uses a page table to keep track of the mapping of virtual address to physical address. In
this example, assume 4KiB pages, a 4-entry fully associative TLB and a LRU (least recently used)
replacement algorithm. The status of the TLB and Page table are shown below
TLB
Valid Dirty Ref Tag
Physical
Page Number
1
0
0
11
12
1
1
1
3
6
1
0
0
5
11
1
0
1
4
9
Page table
Valid
Physical Address
or Disk
GREENHO
0
1
5
0
Disk
0
Disk
1
6
1
9
5
1
11
6
0
Disk
7
1
4
B
0
Disk
9
0
Disk
10
1
3
11
1
12
Example.
Let us assume that the CPU sends the following virtual 4669.
We need to figure out the virtual page number. Since we are using decimal numbers, it is necessary to
perform arithmetic operations
virtual page number =
[virtual address
page size
146691
4096
= 1
This page is NOT in TLB (we check the tags). We check in entry 1 of the page table, this is a not valid
entry (0); this page is NOT in main memory, TLB miss. Thus, we have a page fault.
We need to include the page in page table and TLB.
TLB
Valid Dirty Ref Tag
Physical
Page Number
1
0
0
11
1
1
1
3
S
6
1
0
1
1
7
1
0
1
4
9
Since TLB is fully associative we can place the
new entry in any place. In addition there is a not
valid entry that can be used.
The physical page is provided by the OS. We
can use an address that is not in use; such as 1,
2, 7, let us use 7
Page table
Valid
Physical Address
or Disk
10
OHNM 600 9
1
5
1
7
0
Disk
1
6
1
9
5
1
11
0
Disk
1
4
B
0
Disk
9
0
Disk
1
3
11
1
8
Transcribed Image Text:Let us assume that now the CPU send the following virtual addresses. (Please update TLB and Page table
if needed.)
a) 2227
TLB
Valid Dirty Ref Tag
Page table
Physical Address
Valid
Physical
Page Number
or Disk
0
1
5
1
0
0
11
8
1
1
1
3
I
0
1
1
0
1
314
6
7
9
12345
do
1
7
0
Disk
1
6
1
1
11
6
0
Disk
7
1
4
8
0
Disk
9
о
Disk
10
1
3
11
1
b) 13916 followed by c) 34586 (Initial TLB and Page table status comes from what happen in
(a))
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