Seong-lae ChoSince lack of free frame(low RAM), process > physical memory then page fault rate will be very high
→ os use all time to swapping
Solution Method two - working set, ppf
1. Working set,
locality set + others for continity = working set
Working Set: set of actively used pages
math: \Delta : working-set window : fixed number of page references (ex. 10,000 instruction)ex. WS(t1) = {1,2,3,4,5} ,한꺼번에 반납, 대여
OS monitor direct D, and if D > total number of frames in physical them swap process
then how to direct?: like sampled lru use reference bit and interval time
increasing bit will make performance better 2^bit per interrupt
2. Page-fault Frequency Allocation
Window's method
directly measure and control page-fault rate
establish acceptable page fault frequency
- too high rate → increase number of frames
- too low rate → decrease number of frames