1 Pertemuan 11 Manajemen Memori Matakuliah: T0316/sistem Operasi Tahun: 2005 Versi/Revisi: 5 OFFCLASS02

2 Learning Outcomes Pada akhir pertemuan ini, diharapkan mahasiswa akan mampu : menjelaskan pengelolaan memory dan analisa kinerja multiprogramming (C2)

3 Outline Materi Teknik dasar pengaturan memory Monoprogramming Multi programming dgn Partisi tetap Modeling Multiprogramming Analysis kinerja sistem multiprogramming Relokasi dan proteksi

4 Memory Management Ideally programmers want memory that is –large –fast –non volatile Memory hierarchy –small amount of fast, expensive memory – cache –some medium-speed, medium price main memory –gigabytes of slow, cheap disk storage Memory manager handles the memory hierarchy

5 Basic Memory Management Monoprogramming without Swapping or Paging Three simple ways of organizing memory - an operating system with one user process

6 Multiprogramming with Fixed Partitions Fixed memory partitions –separate input queues for each partition –single input queue

7 Multiprogramming with Fixed Partitions Multiple input queue –When a job arrives, it can be put into the input queue for the smallest partition large enough to hold it Any space in a partition not used by a job is lost The queue for a large partition is empty but the queue for a small partition is full Single input queue –Whenever a partition becomes free, the job closest to the front of the queue that fits in it could be loaded May waste a large partition on a small job –Alternatively  search the whole input queue whenever a partition becomes free and pick the largest job that fits Discriminates against small jobs, whereas the smallest job shall get the best service Solution: –Have at least small partition around –A job may not be skipped for k times

8 Modeling Multiprogramming CPU utilization as a function of number of processes in memory Degree of multiprogramming 1-p n

9 Analysis of Multiprogramming System Performance Arrival and work requirements of 4 jobs CPU utilization for 1 – 4 jobs with 80% I/O wait Sequence of events as jobs arrive and finish –note numbers show amout of CPU time jobs get in each interval

10 Relocation and Protection Cannot be sure where program will be loaded in memory –address locations of variables, code routines cannot be absolute –must keep a program out of other processes’ partitions Use base and limit values –address locations added to base value to map to physical addr –address locations larger than limit value is an error