Operating Systems 2 EN -- OSDI -- 2006-2007 -- info.uvt.ro

Operating Systems 2 EN -- 2006-2007 -- info.uvt.ro

Chapter 4 -- Memory Management

Basic Memory Management
1. Mono-programming without swapping or paging
2. Multi-programing with fixed partitions
  - Fixed memory partitions with separate job queues
  - Fixed memory partitions with a single job queue
3. Relocation and protection
Swapping
- Allocating space for a growing data segment
- Allocating space for a growing stack and data segment
1. Memory management with bitmaps
2. Memory management with linked lists
  - First fit
  - Next fit
  - Best fit
  - Worst fit
  - Quick fit
  - Separate lists for processes and holes
    - Sorted lists by size
Virtual memory
- Overlays
1. Paging
  - Virtual addresses
    - Virtual address space
    - Physical addresses
  - MMU -- Memory Management Unit
  - Pages
    - Virtual page
    - Page frame
  - Page fault
2. Page tables
  - Page number
  - Offset
  - Register page tables
  - Memory page tables
  - Multi-level page tables
  - Structure of a page table entry
    - Page frame number
    - Present / absent
    - Protection
    - Modified
    - Referenced
    - Caching disabled
3. TLB -- Table lookaside buffer
  - Locality of reference
  - TLB fault
4. Inverted Page Tables
Page replacement algorithms
1. Optimal page replacement algorithm
2. NRU -- Not recently used page replacement algorithm
  - Page classes
3. FIFO -- First-in first-out page replacement algorithm
4. Second change page replacement algorithm
5. Clock page replacement algorithm
6. LRU -- Least recently used page replacement algorithm
7. Simulating LRU in software
  - NFU -- Not frequently used