CS403PC Operating System Lec 10 context switching.pptx

1. CS403PC: OPERATING SYSTEM
(R18 II(II Sem))
Department of computer science and engineering
(AI & ML)
LEC 10
by
Asst.Prof.M.Gokilavani
VITS
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2. Syllabus
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4. TEXTBOOK:
• Operating System Principles- Abraham Silberchatz, Peter B.
Galvin, Greg Gagne 7th Edition, John Wiley.
• Advanced programming in the UNIX environment, W.R. Stevens,
Pearson education.
REFERENCES:
• Operating Systems – Internals and Design Principles Stallings,
Fifth Edition–2005, Pearson Education/PHI.
• Operating System A Design Approach- Crowley, TMH.
• Modern Operating Systems, Andrew S. Tanenbaum 2nd edition,
Pearson/PHI.
• UNIX programming environment, Kernighan and Pike, PHI/
Pearson Education.
• UNIX Internals -The New Frontiers, U. Vahalia, Pearson
Education
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5. Topics covered in Lec 10
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UNIT – II: Process and CPU Scheduling - Process
concepts and scheduling, Operations on processes,
Cooperating Processes, Threads, and Interposes
Communication, Scheduling Criteria, Scheduling
Algorithms, Multiple -Processor Scheduling.
System call interface for process management-fork,
exit, wait, waitpid, exec

6. Context Switching
• A context switching is the mechanism to store
and restore the state or context of a CPU in
Process Control block so that a process
execution can be resumed from the same point
at a later time.
• Using this technique, a context switcher
enables multiple processes to share a single
CPU.
• Context switching is an essential part of a
multitasking operating system features.
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8. • When the scheduler switches the CPU from
executing one process to execute another, the
state from the current running process is stored
into the process control block.
• After this, the state for the process to run next
is loaded from its own PCB and used to set the
PC, registers, etc.
• At that point, the second process can start
executing.
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9. • Context switches are computationally intensive
since register and memory state must be saved
and restored.
• To avoid the amount of context switching time,
some hardware systems employ two or more
sets of processor registers.
• When the process is switched, the following
information is stored for later use.
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10. • Program Counter
• Scheduling information
• Base and limit register value
• Currently used register
• Changed State
• I/O State information
• Accounting information
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11. Topics to be covered in next Lec 11
• Operation of Process
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Thank you!!!