Operating systems. (Chapter 10)

Сентябрь 7, 2022

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Operating systems. (Chapter 10)

Содержание

2. Chapter Goals Describe the two main responsibilities of an operating system Define memory and process management
3. Software Categories Application software Software written to address specific needs—to solve problems in the real world
4. Operating System An operating system manages computer resources, such as memory and input/output devices provides an
5. Operating System Figure 10.1 An operating system interacts with many aspects of a computer system.
6. Operating System The various roles of an operating system generally revolve around the idea of “sharing
7. Resource Management Multiprogramming The technique of keeping multiple programs in main memory at the same time
8. Resource Management Process A program in execution The operating system performs process management to carefully track
9. Batch Processing A typical computer in the 1960s and ‘70s was a large machine Its processing
10. Batch Processing Figure 10.2 In early systems, human operators would organize jobs into batches
11. Timesharing Timesharing system A system that allows multiple users to interact with a computer at the
12. Other Factors Real-time System A system in which response time is crucial given the nature of
13. Memory Management Operating systems must employ techniques to Track where and how a program resides in
14. Memory Management Figure 10.3 Memory is a continuous set of bits referenced by specific addresses
15. Single Contiguous Memory Management There are only two programs in memory The operating system The application
16. Single Contiguous Memory Management A logical address is simply an integer value relative to the starting
17. Single Contiguous Memory Management Figure 10.5 binding a logical address to a physical one
18. Partition Memory Management Fixed partitions Main memory is divided into a particular number of partitions Dynamic
19. Partition Memory Management At any point in time memory is divided into a set of partitions,
20. Partition Selection Algorithms Which partition should we allocate to a new program? First fit Allocate program
21. Paged Memory Management Paged memory technique A memory management technique in which processes are divided into
22. Paged Memory Management To produce a physical address, you first look up the page in the
23. Paged Memory Management Demand paging An important extension of paged memory management Not all parts of
24. Paged Memory Management The demand paging approach gives rise to the idea of virtual memory, the
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Chapter Goals
Describe the two main responsibilities of an operating system
Define memory

and process management
Explain how timesharing creates the virtual machine illusion
Explain the relationship between logical and physical addresses
Compare and contrast memory management techniques

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Software Categories
Application software Software written to address specific needs—to solve problems

in the real world
Word processing programs, games, inventory control systems, automobile diagnostic programs, and missile guidance programs are all application software
System software Software that manages a computer system at a fundamental level
It provides the tools and an environment in which application software can be created and run

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Operating System
An operating system
manages computer resources, such as memory and

input/output devices
provides an interface through which a human can interact with the computer
allows an application program to interact with these other system resources

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Operating System
Figure 10.1 An operating system interacts with many aspects of

a computer system.

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Operating System
The various roles of an operating system generally revolve around

the idea of “sharing nicely”
An operating system manages resources, and these resources are often shared in one way or another among programs that want to use them

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Resource Management
Multiprogramming The technique of keeping multiple programs in main memory

at the same time that compete for access to the CPU so that they can execute
Memory management The process of keeping track of what programs are in memory and where in memory they reside

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Resource Management
Process A program in execution
The operating system performs process management

to carefully track the progress of a process and all of its intermediate states
CPU scheduling determines which process in memory is executed by the CPU at any given point

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Batch Processing
A typical computer in the 1960s and ‘70s was a

large machine
Its processing was managed by a human operator
The operator would organize various jobs from multiple users into batches

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Batch Processing
Figure 10.2 In early systems, human operators would organize jobs

into batches

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Timesharing
Timesharing system A system that allows multiple users to interact with

a computer at the same time
Multiprogramming A technique that allows multiple processes to be active at once, allowing programmers to interact with the computer system directly, while still sharing its resources
In a timesharing system, each user has his or her own virtual machine, in which all system resources are (in effect) available for use

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Other Factors
Real-time System A system in which response time is crucial

given the nature of the application
Response time The time delay between receiving a stimulus and producing a response
Device driver A small program that “knows” the way a particular device expects to receive and deliver information.

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Memory Management
Operating systems must employ techniques to
Track where and how a

program resides in memory
Convert logical addresses into actual addresses
Logical address (sometimes called a virtual or relative address) A value that specifies a generic location, relative to the program but not to the reality of main memory
Physical address An actual address in the main memory device

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Memory Management
Figure 10.3 Memory is a continuous set of bits referenced

by specific addresses

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Single Contiguous Memory Management
There are only two programs in memory
The operating

system
The application program
This approach is called single contiguous memory management

Figure 10.4 Main memory divided into two sections

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Single Contiguous Memory Management
A logical address is simply an integer value

relative to the starting point of the program
To produce a physical address, we add a logical address to the starting address of the program in physical main memory

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Single Contiguous Memory Management
Figure 10.5 binding a logical address to a

physical one

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Partition Memory Management
Fixed partitions Main memory is divided into a particular

number of partitions
Dynamic partitions Partitions are created to fit the needs of the programs

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Partition Memory Management
At any point in time memory is divided into

a set of partitions, some empty and some allocated to programs
Base register A register that holds the beginning address of the current partition
Bounds register A register that holds the length of the current partition

Figure 10.6 Address resolution in partition memory management

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Partition Selection Algorithms
Which partition should we allocate to a new program?
First

fit Allocate program to the first partition big enough to hold it
Best fit Allocated program to the smallest partition big enough to hold it
Worst fit Allocate program to the largest partition big enough to hold it

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Paged Memory Management
Paged memory technique A memory management technique in which

processes are divided into fixed-size pages and stored in memory frames when loaded into memory
Frame A fixed-size portion of main memory that holds a process page
Page A fixed-size portion of a process that is stored into a memory frame
Page-map table (PMT) A table used by the operating system to keep track of page/frame relationships

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Paged Memory Management
To produce a physical address, you first look up

the page in the PMT to find the frame number in which it is stored
Then multiply the frame number by the frame size and add the offset to get the physical address

Figure 10.7 A paged memory management approach

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Paged Memory Management
Demand paging An important extension of paged memory management
Not

all parts of a program actually have to be in memory at the same time
In demand paging, the pages are brought into memory on demand
Page swap The act of bringing in a page from secondary memory, which often causes another page to be written back to secondary memory

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Paged Memory Management
The demand paging approach gives rise to the idea

of virtual memory, the illusion that there are no restrictions on the size of a program
Too much page swapping, however, is called thrashing and can seriously degrade system performance.

Operating systems. (Chapter 10)

Содержание

Chapter GoalsDescribe the two main responsibilities of an operating systemDefine memory

Software CategoriesApplication software Software written to address specific needs—to solve problems

Operating SystemAn operating system manages computer resources, such as memory and

Operating SystemFigure 10.1 An operating system interacts with many aspects of

Operating SystemThe various roles of an operating system generally revolve around

Resource ManagementMultiprogramming The technique of keeping multiple programs in main memory

Resource ManagementProcess A program in executionThe operating system performs process management

Batch ProcessingA typical computer in the 1960s and ‘70s was a

Batch ProcessingFigure 10.2 In early systems, human operators would organize jobs

TimesharingTimesharing system A system that allows multiple users to interact with

Other FactorsReal-time System A system in which response time is crucial

Memory ManagementOperating systems must employ techniques toTrack where and how a

Memory ManagementFigure 10.3 Memory is a continuous set of bits referenced

Single Contiguous Memory ManagementThere are only two programs in memoryThe operating

Single Contiguous Memory ManagementA logical address is simply an integer value

Single Contiguous Memory ManagementFigure 10.5 binding a logical address to a

Partition Memory ManagementFixed partitions Main memory is divided into a particular

Partition Memory ManagementAt any point in time memory is divided into

Partition Selection AlgorithmsWhich partition should we allocate to a new program?First

Paged Memory ManagementPaged memory technique A memory management technique in which

Paged Memory ManagementTo produce a physical address, you first look up

Paged Memory ManagementDemand paging An important extension of paged memory managementNot

Paged Memory ManagementThe demand paging approach gives rise to the idea

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