An inactive unit, such as a file stored on a disk
To an OS, this is a unit of work that has been submitted by the user
program
An active entity that requires a set of resources, including a processor and special registers, to perform its function.
Also called a task, is a single instance of a program in execution
Process
A portion of a process that can run indepen
dently
thread
The part of the machine that performs the calculations and executes the programs.
processor
Was driven by the problems caused by nano-sized transistors and their ultra-close placement on a computer chip
multi-core engineering
Solution to the problem of the amount of heat generated by a chip
Single chip with two or more processor cores
The Processor Manager is a composite of two submanagers: one in charge of job scheduling and the other in charge of process scheduling. They’re known as the _______ and the __________
Job Scheduler, Process Scheduler
also called as the high-level scheduler
Job Scheduler
also called as the low-level scheduler
Process Scheduler
In a highly interactive environment, there’s also a third layer of the Processor Manager called the ___________
middle-level scheduler
five states of job status or process status
HOLD to READY to RUNNING to WAITING and eventually to FINISHED
As a job moves through the system, it’s always in one of five state. These are called:
job status or process status
Each process in the system is represented by a data structure called a:
Process Control Block (PCB)
Contains the basic information about the job, including what it is, where it’s going, how much of its processing has been completed, where it’s stored, and how much it has spent in using resources
Process Control Block (PCB)
Contents of each job’s Process Control Block.
- Process identification
- Process status
- Process state:
- Process status word
- Register contents
- Main memory
- Resources
-Process priority - Accounting
Each job is uniquely identified by the user’s identification and a pointer connecting it to its descriptor
Process Identification
This indicates the current status of the job—HOLD, READY, RUNNING, or WAITING—and the resources responsible for that status.
Process Status
This contains all of the information needed to indicate the current state of the job
Process State
This contains information used mainly for billing purposes and performance measurement
Accounting
It use PCBs to track jobs the same way customs officials use passports to track international visitors
Queues
Before the operating system can schedule them, it needs to resolve three limitations of the system:
(1) there are a finite number of resources (such as disk drives, printers, and tape drives);
(2) some resources, once they’re allocated, can’t be shared with another job (e.g., printers);
(3) some resources require operator intervention—that is, they can’t be reassigned automatically from job to job (such as tape drives)
Good process scheduling policy criterias
- Maximize throughput
- Minimize response time
- Minimize turnaround time
- Minimize waiting time
- Maximize CPU efficiency
- Ensure fairness for all jobs
A scheduling strategy that interrupts the processing of a job and transfers the CPU to another job is called a ________________
preemptive scheduling policy
Alternative of preemptive scheduling policy, which functions without external interrupts
nonpreemptive scheduling policy
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Chapter 1103
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Chapter 25
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Review Questions13
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Chapter 361
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Chapter 441
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Key Terms79
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Chapter 527
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Chapter 5 key terms19
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Chapter 3 Key Terms32
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Chapter 4 Key Terms37
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Chapter 2 Key Terms18
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Chapter 1 Key Terms32
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Chapter 645
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Chapter 6 Key Terms25
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Chapter 756
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Chapter 7 Key Terms42
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Chapter 8 Key Terms33
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Chapter 847
