Chapter-04

Chapter-04 - Chapter 4 Memory Management 4.1 Basic memory...

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1 Memory Management Chapter 4 4.1 Basic memory management 4.2 Swapping 4.3 Virtual memory 4.4 Page replacement algorithms 4.5 Modeling page replacement algorithms 4.6 Design issues for paging systems 4.7 Implementation issues 4.8 Segmentation
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2 Agenda 4.1 Basic memory management 4.2 Swapping 4.3 Virtual memory 4.4 Page replacement algorithms 4.5 Modeling page replacement algorithms 4.6 Design issues for paging systems 4.7 Implementation issues 4.8 Segmentation
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3 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
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4 Basic Memory Management Monoprogramming without Swapping or Paging Three simple ways of organizing memory - an operating system with one user process Mainframes and Minicomputers PDAs and Embedded Systems PCs and MS-DOS
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5 Multiprogramming with Fixed Partitions Fixed memory partitions separate input queues for each partition single input queue Used for many years on OS/360 or OS/MFT (Multiprogramming with Fixed number of Tasks)
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6 Modeling Multiprogramming CPU utilization as a function of number of processes in memory Degree of multiprogramming CPU Utilization = 1 – p n
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7 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
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8 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
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9 Agenda 4.1 Basic memory management 4.2 Swapping 4.3 Virtual memory 4.4 Page replacement algorithms 4.5 Modeling page replacement algorithms 4.6 Design issues for paging systems 4.7 Implementation issues 4.8 Segmentation
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10 Motivation Fixed memory partitions Good for batch systems Simple and effective For Time Sharing systems and PCs There may not be enough main memory to hold all the currently active processes. Therefore, excess processes must be kept on disk and brought in to run dynamically.
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11 Swapping (1) Memory allocation changes as processes come into memory leave memory Shaded regions are unused memory
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12 Swapping (2) Allocating space for growing data segment Allocating space for growing stack & data segment
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13 Memory Management with Bit Maps Part of memory with 5 processes, 3 holes tick marks show allocation units shaded regions are free Corresponding bit map Same information as a list
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14 Memory Management with Linked Lists Four neighbor combinations for the terminating process X
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This note was uploaded on 09/15/2011 for the course CDA 4610 taught by Professor Sadjadi during the Fall '09 term at FIU.

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Chapter-04 - Chapter 4 Memory Management 4.1 Basic memory...

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