2. OPERATING SYSTEM
Program to manage Computer Hardware.
Provide base for Application programs.
Acts as an intermediary between user and hardware.
Supports Complex games, business applications, etc. .
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3. Process - Definition
Is simply a Program in Execution.
Unit of work in most system.
Consist of collection of processes like Word processing, System task etc.
Processes executes concurrently.
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4. NEED OF
PROCESS MANAGEMENT
Manage the processes of OS
Integral part of modern day OS.
Multitasking – Multiple task at single time.
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5. Process State
New – Process is being created.
Running – Instruction are being executed.
Waiting – Waiting for some event to occur.
Ready – Process is ready to be assigned to a processor.
Blocked - Due to Exhausting CPU time allocation.
Terminated – After completion of execution.
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7. Process Control Block
Contains many pieces of information associated with a specific process
Process Identification Data : include unique identifier for the process.
Processor State Data : Defines the status of process.
Process control data : Used by OS to manage the process itself.
Threads : Smallest sequence of programmed instructions.
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8. Process Scheduling
Activity of process manager that handles the removal of the running process from
CPU.
Scheduling Queues : Consist of all processes.
Schedulers : Migrate between various Scheduling Queues.
Context Switch : Stopping of one and starting of another process.
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9. THREADS
Smallest sequence of programmed instructions.
Called a Lightweight Process.
Basic unit of CPU Utilization.
Basic component of process.
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10. Multithreading Models
Many-to-one Model : Maps many user level thread to one kernel thread.
One-to-one Model : Maps each user thread to kernel thread.
Many-to-many Model : Maps many user level thread to smaller or equal
Number of kernel thread.
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11. Scheduling Algorithm
This defines the schedules for Processes to be executed in which manner.
These are of four types :
FCFS : First-Come First-Serve basis.
SJF : Shortest Job First
Priority Scheduling
Round-Robin Scheduling
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12. First Come First Serve
Process Burst Time
P1 24
P2 3
P3 3
Matters with who comes first whatever is condition.
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13. Shortest Job First
Process Arrival Time Burst Time
P1 0.0 6
P2 0.0 4
P3 0.0 1
P4 0.0 5
Matters with Expected time for burst (execution).
If required Priority, FCFS is used to break.
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14. Priority Scheduling
Works according to Priority.
Highest priority executes first.
Equal priority scheduled in FCFS order.
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15. Round Robin Scheduling
Process Burst Time
P1 53
P2 17
P3 68
P4 24
Each process gets a small unit of CPU time.
Equal priority scheduled in FCFS order.
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16. Deadlocks
Several Process compete for resources. If resource is available, it goes for execution
if it is unavailable, it enters in wait state. Waiting process never change state as
requested resources are held by other waiting processes, this situation is Called
Deadlock.
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