FIT2100 Lecture Notes - Lecture 8: Logical Address, Modular Programming, Memory Management
31 May 2018
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Lecture 8,9 & 10/Tute 6 - Memory Management, I/O Management and Disk Scheduling
Memory Management (Lecture 8)
Main memory is divided into two parts:
-One part for OS (kernel)
-One part for the program currently running
Multiprogramming:
-‘User’ part of memory is further subdivided to accommodate multiple processes
Terminology:
-Frame — a fixed-length block of main memory
-Page — a fixed-length black of data that resided in secondary memory
-Segment — a variable-length block of data that resides in secondary memory
Memory Management: Requirements
-Memory management is intended to satisfy the following requirements in order to support
multitasking or multiprogramming systems
-Relocation
-Active processes need to be able to be swapped in and out of main memory in order to
maximise processor utilisation
-Specifying that a process must be placed in the same memory region when it is swapped
back in would be limiting — may need to relocate the process to a different area of
memory
-Protection
-Processes need to acquire permission to reference memory locations for reading or writing
purposes
-Location of a program in main memory is unpredictable
-Memory references generated by a process my be checked at run time by the processor
-Mechanisms that support relocation also support protection
-Sharing
-Advantageous to allow each process access to the same copy of the program rather than
have their own separate copy
-Memory management must allow controlled access to shared areas of memory without
compromising protection
-Mechanisms that support relocation also support sharing capabilities
-Logical organisation
-Memory (main and secondary) is typically organised linear
-Segmentation: the tool that most readily satisfies requirements
-Physical organisation
-Cannot leave the programmer with the responsibility to manage memory
-Memory available for a program plus its data may.be insufficient
-Programmer does not know how much space will be available
Memory Partitioning
-Memory management brings processes into main memory for execution by the processor
-Involves virtual memory
-Based on segmentation and paging
Partitioning
-Used in several variations in some now-obsolete operating systems
-Does not involve virtual memory
Memory Management: Techniques
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Lecture 8,9 & 10/tute 6 - memory management, i/o management and disk scheduling. One part for the program currently running. User" part of memory is further subdivided to accommodate multiple processes. Frame a fixed-length block of main memory. Page a fixed-length black of data that resided in secondary memory. Segment a variable-length block of data that resides in secondary memory. Memory management is intended to satisfy the following requirements in order to support multitasking or multiprogramming systems. Active processes need to be able to be swapped in and out of main memory in order to maximise processor utilisation. Specifying that a process must be placed in the same memory region when it is swapped back in would be limiting may need to relocate the process to a different area of memory. Processes need to acquire permission to reference memory locations for reading or writing purposes. Location of a program in main memory is unpredictable.
