Classroom slides memory systems

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Classroom slides memory systems
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PCB

• enum state_type new, ready, running,
  waiting, halted
• typedef struct control_block_type
• enum state_type state
• address PC
• int reg_fileNUMREGS
• struct control_block next_pcb
• int priority
• address memory_footprint ????
• .
• .
• control_block

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PCB

• enum state_type new, ready, running,
  waiting, halted
• typedef struct control_block_type
• enum state_type state
• address PC
• int reg_fileNUMREGS
• struct control_block next_pcb
• int priority
• address memory_footprint ????
• .
• .
• control_block

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Fixed size partitions
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Variable size partitions
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New request P4 needs 4K Possible?
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Compaction
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Paging and virtual memory
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Physical Memory
LOW
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Page Table
Users view
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Page 0
35
Page 1
52
12
Page 2
Page 3
15
35
52
HIGH
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Address translation
Virtual Address
Physical Address
Memory
VPN
Page offset
PPN
Page offset
CPU
PPN
Page table
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• Example 1
• Consider a memory system with a 32-bit
  virtual address. Let us assume the pagesize is
  8K Bytes.
• Example 2
• Consider a memory system with 32-bit virtual
  addresses and 24-bit physical memory addresses.
  Assume that the pagesize is 4K Bytes. Show the
  layout of the virtual and physical addresses.
  How big is the page table? How many page frames
  are there in this memory system?

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PCB

• enum state_type new, ready, running,
  waiting, halted
• typedef struct control_block_type
• enum state_type state
• address PC
• int reg_fileNUMREGS
• struct control_block next_pcb
• int priority
• address PTBR
• .
• .
• control_block

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Freelist
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Frame Table
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Disk Map
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• Example
• process P1 page fault at VPN 20.
• free-list is empty.
• selects page frame PFN 52 as the victim.
• frame currently houses VPN 33 of process P4.

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FIFO Page Replacement
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Consider a string of page references by a
process Reference number 1 2 3 4 5
6 7 8 9 10 11 12 13
-------------------------------
--------------------------- Virtual page number
9 0 3 4 0 5 0 6 4 5 0
5 4 Assume there are 3 physical frames.
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Reference 1 (PF)
Reference 2 (PF)
9
Head
9
Head
free
0
Full false
Full false
free
free
Tail
Tail
Reference 3 (PF)
Reference 4 (PF)
9
4
Head
Head
0
0
Full true
Full true
3
3
Tail
Tail
Reference 5 (HIT)
Reference 6 (PF)
4
4
Head
Head
0
5
Full true
Full true
3
3
Tail
Tail
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Consider a string of page references by a
process Reference number 1 2 3 4 5
6 7 8 9 10 11 12 13
-------------------------------
--------------------------- Virtual page number
9 0 3 4 0 5 0 6 4 5 0
5 4
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Beladys Min
Consider a string of page references by a
process Reference number 1 2 3 4 5
6 7 8 9 10 11 12 13
-------------------------------
--------------------------- Virtual page number
9 0 3 4 0 5 0 6 4 5 0
5 4
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LRU
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Consider a string of page references by a
process Reference number 1 2 3 4 5
6 7 8 9 10 11 12 13
-------------------------------
--------------------------- Virtual page number
9 0 3 4 0 5 0 6 4 5 0
5 4 Assume there are 3 physical frames.
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Reference 1 (PF)
Reference 2 (PF)
9
Top
0
Top
free
9
free
Bottom
free
Bottom
Reference 3 (PF)
Reference 4 (PF)
3
Top
4
Top
0
3
9
Bottom
0
Bottom
Reference 5 (HIT)
Reference 6 (PF)
0
Top
5
Top
4
0
3
Bottom
4
Bottom
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Approximate LRU with ref bits
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Optimizations
victim
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TLB
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TLB Hit
Physical Memory
CPU
VPN
Offset
TLB
VPN
PPN
PPN
Offset
VPN
PPN
VPN
PPN
VPN
PPN
VPN
PPN
Page Table
VPN
PPN
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TLB Miss
Physical Memory
CPU
VPN
Offset
TLB
VPN
PPN
PPN
Offset
VPN
PPN
VPN
PPN
VPN
PPN
VPN
PPN
Page Table
VPN
PPN
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TLB Hit
Physical Memory
CPU
Page
Offset
TLB
Page
Frame
Frame
Offset
Page
Frame
Page
Frame
Page
Frame
Page
Frame
Page Table
Page
Frame
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