Process Control Block
Threads & Their Management
By Ujjwal Kumar
1149210055
CS – V – 2013
Process Control
Block
or
PCB
Presentation by Ujjwal
Kumar
2
Introduction
• Each & every process in the Operating System is
represented by a Process Control Block.
• Process Control B...
What exactly is PCB?
• It is a Data Structure in the operating system
kernel containing the information needed to
manage a...
Presentation by Ujjwal
Kumar
5
Source: http://lmgtfy.com/?q=define%3Amanifestation/
Presentation by Ujjwal
Kumar
6
Fig: Process Control Block (PCB)
What exactly does this
diagram mean?
Presentation by Ujjwal
Kumar
7
• Pointers: It contains the address of another
process which is present in the ready queue.
• Process State: It contains i...
• Program Counter: The address of the next
instruction to be executed.
• CPU Registers: The registers vary in no. and
type...
• CPU scheduling information: This
information includes
▫ Process priority
▫ Pointer to scheduling queues
▫ Other scheduli...
• Accounting information: This information
includes
• Amount of CPU and real time used
• Time limits
• Account numbers
• J...
Now we know what exactly the
Process Control Block is. But
do we know where the location
of PCB is?
Presentation by Ujjwal...
• Contains critical information of processes and
hence it must be placed where it is protected
from normal user access.
• ...
Interleaving
Execution of
Processes
Presentation by Ujjwal
Kumar
14
Interleaving Execution of Processes
• Perception of normal end user:
Presentation by Ujjwal
Kumar
15
Process
A Process
B
P...
Interleaving Execution of Processes
• In reality, this is how the processes are executed:
Presentation by Ujjwal
Kumar
16
...
Threads &
their Management
Presentation by Ujjwal
Kumar
17
Threads
• Definition: In simple words we can say that
Threads are light weight processes.
• It is a sequence and not a pro...
Advantages of Threads
• If a process has multiple threads then it will be
able to perform more than one single task at the...
Types of Threading
•Single Threading
•Multi Threading
Presentation by Ujjwal
Kumar
20
Multithreading
• Sometimes several similar tasks have to be
performed by the application in order to get the
word done.
• ...
Real life examples of Multithreading - I
• Web browsers: They have different threads to
do different work.
▫ One thread wi...
Real life examples of Multithreading -
II
• Word Processors: Different threads in word
processor will do different jobs.
▫...
Benefits of Multithreading
• Responsiveness: The process responds much
better while using multithreading as compared
to si...
• Utilization in multiprocessor systems:
▫ Multithreading can take advantages of a
multiprocessor system.
▫ Multiple threa...
Implementation of Threads
• Threads are implemented in a system in three
different ways.
▫ Kernel Level Threads
▫ User Lev...
Kernel Level Threads
• Implemented by the kernel itself.
• Management of threads is also done by the
kernel itself.
Presen...
User Level Thread
Presentation by Ujjwal
Kumar
28
Kernel Space
Thread
Table
Thread
Process
User
Space
User Level Thread
• These type of threads are loaded in the user
space and the kernel doesn’t have anything to do
with thi...
Acknowledgements
• Sir. Mukesh Kumar Singh
• Google.com
• Book: OS by Vijay Shukla
Presentation by Ujjwal
Kumar
30
Questions
You can ask any questions
you might have in your
mind related to my
presentation.
Presentation by Ujjwal
Kumar
31
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  • In this we will see how the processes are executed by the PCB. Let us first discuss how a normal end user sees the processes being executed.
  • The processes are done in order of priority so there is no specific order.
  • Hybrid level thread is out of syllabus so we will not discuss it.
  • Process Control Block & Threads and Their Management

    1. 1. Process Control Block Threads & Their Management By Ujjwal Kumar 1149210055 CS – V – 2013
    2. 2. Process Control Block or PCB Presentation by Ujjwal Kumar 2
    3. 3. Introduction • Each & every process in the Operating System is represented by a Process Control Block. • Process Control Block ~ Task Control Block or Task Struct. 3 Presentation by Ujjwal Kumar
    4. 4. What exactly is PCB? • It is a Data Structure in the operating system kernel containing the information needed to manage a particular process. • The PCB is "the manifestation(Visible) of a process in an operating system” 4 Presentation by Ujjwal Kumar
    5. 5. Presentation by Ujjwal Kumar 5 Source: http://lmgtfy.com/?q=define%3Amanifestation/
    6. 6. Presentation by Ujjwal Kumar 6 Fig: Process Control Block (PCB)
    7. 7. What exactly does this diagram mean? Presentation by Ujjwal Kumar 7
    8. 8. • Pointers: It contains the address of another process which is present in the ready queue. • Process State: It contains information about the state of the process i.e., • New • Ready • Running • Waiting • Halted Presentation by Ujjwal Kumar 8
    9. 9. • Program Counter: The address of the next instruction to be executed. • CPU Registers: The registers vary in no. and type depending on the type of computer architecture, they include: • Accumulators, index registers, stack pointers and general purpose registers Presentation by Ujjwal Kumar 9
    10. 10. • CPU scheduling information: This information includes ▫ Process priority ▫ Pointer to scheduling queues ▫ Other scheduling parameters. • Memory management information: This information includes ▫ Value of base and limit registers ▫ Page tables ▫ Segment tables. Presentation by Ujjwal Kumar 10
    11. 11. • Accounting information: This information includes • Amount of CPU and real time used • Time limits • Account numbers • Job or Process numbers etc. • I/O status information: This information includes • List of I/O devices allocated to the process • List of open files etc . Presentation by Ujjwal Kumar 11
    12. 12. Now we know what exactly the Process Control Block is. But do we know where the location of PCB is? Presentation by Ujjwal Kumar 12
    13. 13. • Contains critical information of processes and hence it must be placed where it is protected from normal user access. • In many Operating systems, it is placed in the beginning of the kernel stack of the process since that is a convenient protected location. Presentation by Ujjwal Kumar 13
    14. 14. Interleaving Execution of Processes Presentation by Ujjwal Kumar 14
    15. 15. Interleaving Execution of Processes • Perception of normal end user: Presentation by Ujjwal Kumar 15 Process A Process B Process C Process D Time
    16. 16. Interleaving Execution of Processes • In reality, this is how the processes are executed: Presentation by Ujjwal Kumar 16 Process 1 Process 2 Process 1 Process 2
    17. 17. Threads & their Management Presentation by Ujjwal Kumar 17
    18. 18. Threads • Definition: In simple words we can say that Threads are light weight processes. • It is a sequence and not a program because it cannot run on its own so it returns within the program. • A process is divided into smaller tasks and these tasks are known as threads. • A basic unit of CPU Utilization. Presentation by Ujjwal Kumar 18
    19. 19. Advantages of Threads • If a process has multiple threads then it will be able to perform more than one single task at the same time. • Better Throughput. • Makes the program Responsive. Presentation by Ujjwal Kumar 19
    20. 20. Types of Threading •Single Threading •Multi Threading Presentation by Ujjwal Kumar 20
    21. 21. Multithreading • Sometimes several similar tasks have to be performed by the application in order to get the word done. • This is where the Multithreading comes in. Presentation by Ujjwal Kumar 21
    22. 22. Real life examples of Multithreading - I • Web browsers: They have different threads to do different work. ▫ One thread will retrieve data from the remote servers. ▫ Another one will render the data received into visual web pages. • Example: Google Chrome, Opera, Firefox etc. Presentation by Ujjwal Kumar 22
    23. 23. Real life examples of Multithreading - II • Word Processors: Different threads in word processor will do different jobs. ▫ One will render the text based materials. ▫ Another one will render graphic based materials like the images etc. • Example: Microsoft Office Presentation by Ujjwal Kumar 23
    24. 24. Benefits of Multithreading • Responsiveness: The process responds much better while using multithreading as compared to single threaded processes. • Speed Up: The process is speeded up by using multithreading hence giving a much better experience to the end user. • Efficient Communication: The threads of a specific process can communicate with each other efficiently because of the shared address space. Presentation by Ujjwal Kumar 24
    25. 25. • Utilization in multiprocessor systems: ▫ Multithreading can take advantages of a multiprocessor system. ▫ Multiple threads can be processed on multiple cores of the system. Presentation by Ujjwal Kumar 25
    26. 26. Implementation of Threads • Threads are implemented in a system in three different ways. ▫ Kernel Level Threads ▫ User Level Threads ▫ Hybrid Level Threads Presentation by Ujjwal Kumar 26
    27. 27. Kernel Level Threads • Implemented by the kernel itself. • Management of threads is also done by the kernel itself. Presentation by Ujjwal Kumar 27 Process Threads Process Table
    28. 28. User Level Thread Presentation by Ujjwal Kumar 28 Kernel Space Thread Table Thread Process User Space
    29. 29. User Level Thread • These type of threads are loaded in the user space and the kernel doesn’t have anything to do with this. • Threads are managed in user space so each process must have its own private thread table. • This table consists the information of: ▫ Program Counter ▫ Stack Pointer ▫ Register. Presentation by Ujjwal Kumar 29
    30. 30. Acknowledgements • Sir. Mukesh Kumar Singh • Google.com • Book: OS by Vijay Shukla Presentation by Ujjwal Kumar 30
    31. 31. Questions You can ask any questions you might have in your mind related to my presentation. Presentation by Ujjwal Kumar 31
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