1 Pertemuan 15 Modelling Page Replacement Algorithm Matakuliah: T0316/sistem Operasi Tahun: 2005 Versi/Revisi: 5
2 Learning Outcomes Pada akhir pertemuan ini, diharapkan mahasiswa akan mampu : menjelaskan permodelan algoritma pergantian page dan memprediksi page fault (C2)
3 Outline Materi Belady's Anomali Stack Algorithm Distance String Memprediksi Page fault
4 Modeling Page Replacement Algorithms Belady's Anomaly FIFO with 3 page frames FIFO with 4 page frames P's show which page references show page faults
5 Stack Algorithms State of memory array, M, after each item in reference string is processed
6 Stack Algorithms (2) Stack algorithm has the property of M(m, r) M(m+1, r) where M internal array m number of page frames n virtual pages r index into the reference string The set of pages included in the top part of M for a memory with m page frames after r memory references are also included in M for a memory with m+1 page frames LRU has this property but FIFO does not This algorithm do not suffer from Belady’s Anomaly m n … r …
7 The Distance String Probability density functions for two hypothetical distance strings
8 The Distance String Computation of page fault rate from distance string –the C vector –the F vector