[OS]Virtual memory management

Virtual memory

• Non-continuous allocation
• Paging/Segmentation system

Cost Model for Virtual Mem. Sys.

• Page fault frequency
• Page fault rate

Hardware Components

• Address translation device
  • TLB(associated memories), Dedicated page-table register, Cache memories
• Bit Vectors
  • Reference bits(used bit)
  • Update bits(modified bits, write bits, dirty bits)

Software Components

• Allocation strategies
• Fetch strategies
• Placement strategies
• Replacement strategies
• Cleaning strategies
• Load control strategies

Replacement Strategies

• Fixed allocation
  • MIN(OPT, B0) algorithm
  • Random algorithm
  • FIFO(First In First Out) algorithm
  • LRU(Least Recently Used) algorithm
  • LFU(Least Frequently Used) algorithm
  • NUR(Not Used Recently) algorithm
  • Clock algorithm
  • Second chance algorithm
• Variable allocation
  • WS(Working Set) algorithm
  • PFF(Page Fault Frequency) algorithm
  • VMIN(Variable MIN) algorithm

Other Considerations

• Page size
• Program restructuring
• TLB reach

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Reference

Virtural memory management