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CH 10: Virtual Memory - Coggle Diagram
CH 10: Virtual Memory
Page Replacement
modify bit (when page is modified)
Algorithm
FIFO
Optimal
LRU
Second-chance
Counting
LFU
MFU
Global Allocation
Reclaiming Pages
Local Allocation
Demand Paging
Pager
MMU functionality
Bring necessary pages
Not in the memory? load the page from the storage
Extreme case (Pure demand paging)
locality of reference
Instruction restart
Copy-on-Write
share same pages
creates copy when needed to modify
zero-fill-on-demand
parents and child processes
vfork(): child share same memory with parents
Allocation of Frames
Free-Frame List
zero-fill-on-demand
Activities
Service the interrupt
Read the page
Restart the process
Fixed Allocation
Equal allocation
Proportional allocation
Thrashing
Working-Set Model
Keeps track how many
pages a proces actually needs
Page-Fault Frequency
Keeps track page fault frequncy
Too high -> more frames
Too low -> less frame
Allocating Kernel Memory
Buddy System
split into smaller chunks
round up next higher the power of 2
Slab Allocator
cache
objects (data)
Non-Uniform Memory Access (NUMA)
different speed of access to memory
solved by using lgroups
Background
Partially-loaded program
Memory-Mapped Files