Allocation of Frames¶

Allocation Policies¶

Fixed allocation
- Equal allocation : 100 frames and 5 processes, then allocate 20 frames per processes
- Proportional allocation: Allocate according to the size of the process
Priority allocation
- Using propotional allocation based on priority, instead of size
- if process P generates a page fault
  - select for replacement one of its frames
  - select for replacement from a process with lower priority
Local allocation : each process select from its own set of allocated frames
Global allocation : process selects a replacement frame frome the set of all frames
- one process can take away a frame of another process
- e.g., allow a high-priority process to take frames from a low-priority process
- good system performance and thus is common used
- A minimum number of frames must be maintained for each process to prevent thrashing