Lecture9

Operating System Lecture 9 : Virtual Memory (462271) ,[object Object],[object Object],[object Object],[object Object]

Contents ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Background ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Virtual Memory That is Larger Than Physical Memory 

Virtual-address Space ,[object Object],[object Object],[object Object],[object Object],[object Object]

Shared Library Using Virtual Memory ,[object Object]

Demand Paging ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Demand Paging ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Transfer of a Paged Memory to Contiguous Disk Space ,[object Object],[object Object]

Valid-Invalid Bit ,[object Object],[object Object],[object Object],[object Object],[object Object],v v v v i i i … . Frame # valid-invalid bit page table

Page Table When Some Pages Are Not in Main Memory ,[object Object]

Hardware Instruction Processing Algorithm ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Page Fault ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Steps in Handling a Page Fault ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Page Fault Handler Algorithm ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Sequence occurs caused by a Page fault ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Performance of Demand Paging ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Process Creation ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Copy-on-Write ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Memory-Mapped Files ,[object Object],[object Object],[object Object],[object Object]

What happens if there is no free frame? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Page Replacement ,[object Object],[object Object],[object Object],[object Object],[object Object]

Need For Page Replacement ,[object Object],2. ไม่มีเฟรมว่าง

Basic Page Replacement ,[object Object],[object Object],[object Object],[object Object]

Page Replacement Algorithms ,[object Object],[object Object],[object Object],[object Object],[object Object],Graph of Page Faults Versus The Number of Frames

First-In-First-Out (FIFO) Algorithm ,[object Object],[object Object],[object Object]

FIFO Illustrating Belady’s Anomaly ,[object Object]

FIFO Page Replacement ,[object Object],[object Object],[object Object]

Optimal Algorithm ,[object Object],[object Object],[object Object],[object Object],[object Object],1 2 3 4 6 page faults 4 5

Optimal Page Replacement ,[object Object],[object Object],[object Object],[object Object]

Least Recently Used (LRU) Algorithm ,[object Object],[object Object],[object Object],5 2 4 3 1 2 3 4 1 2 5 4 1 2 5 3 1 2 4 3

LRU Algorithm ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Use Of A Stack to Record The Most Recent Page References

LRU - Clock ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

LRU- Second Chance (clock) Page Replacement

LRU- Second Chance (clock) Page Replacement (2)

LRU- Second Chance (clock) Page Replacement (3)

Enhanced Second-Chance Algorithm ,[object Object],Counting Algorithms ,[object Object],[object Object],[object Object], Modified Referenced Meaning Case 1 0 0 Not modified AND not referenced Case 2 0 1 Not modified BUT was referenced Case 3 1 0 Was modified BUT not referenced (impossible?) Case 4 1 1 Was modified AND referenced

Page Replacement Policy - Bit-shifting ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Allocation of Frames ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Allocation of Frames ,[object Object],[object Object],[object Object],[object Object],[object Object]

Thrashing ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Thrashing (Cont.) ,[object Object],[object Object],[object Object],[object Object]

Locality In A Memory-Reference Pattern ,[object Object],[object Object],[object Object],[object Object]

Working-Set Model ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Working-Set Model ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Page-Fault Frequency Scheme ,[object Object],[object Object],[object Object],[object Object]

Allocating Kernel Memory ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Buddy System ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Slab Allocator ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Other Issues – Prepaging & Page Size ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Other Issues – TLB Reach ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Other Issues – Program Structure ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Other Issues – I/O interlock ,[object Object],[object Object],Reason Why Frames Used For I/O Must Be In Memory

Other Issues – Real-Time Processing ,[object Object],[object Object],[object Object],[object Object],[object Object]

Summary ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Lecture9

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