1 Pertemuan 13 Algoritma Pergantian Page Matakuliah: T0316/sistem Operasi Tahun: 2005 Versi/Revisi: 5.

Presentasi berjudul: "1 Pertemuan 13 Algoritma Pergantian Page Matakuliah: T0316/sistem Operasi Tahun: 2005 Versi/Revisi: 5."— Transcript presentasi:

1 1 Pertemuan 13 Algoritma Pergantian Page Matakuliah: T0316/sistem Operasi Tahun: 2005 Versi/Revisi: 5

2 2 Learning Outcomes Pada akhir pertemuan ini, diharapkan mahasiswa akan mampu : menjelaskan cara kerja algoritma pergantian page (C2)

3 3 Outline Materi Page replacement algorithms –Optimal –Not Recently used –FIFO –Second chance

4 4 Page Replacement Algorithms Page fault forces choice –which page must be removed –make room for incoming page Modified page must first be saved –unmodified just overwritten Better not to choose an often used page –will probably need to be brought back in soon

5 5 Optimal Page Replacement Algorithm Replace page needed at the farthest point in future –Optimal but unrealizable Estimate by … –logging page use on previous runs of process –although this is impractical

6 6 Optimal  Contoh 7012030421071 70707 107107 102102 102102 302302 302302 402402 402402 401401 401401 471471 471471

7 7 Not Recently Used Each page has Reference bit, Modified bit –bits are set when page is referenced, modified Pages are classified 1.not referenced, not modified 2.not referenced, modified 3.referenced, not modified 4.referenced, modified NRU removes page at random –from lowest numbered non empty class

8 8 FIFO Maintain a linked list of all pages –in order they came into memory Page at beginning of list replaced Disadvantage –page in memory the longest may be often used

9 9 FIFO  Contoh 7012030421071 70707 107107 210210 210210 321321 032032 403403 240240 124124 012012 701701 170170

10 10 Second Chance Operation of a second chance –pages sorted in FIFO order –Page list if fault occurs at time 20, A has R bit set (numbers above pages are loading times)