Transcript review-midterm

Operating Systems
Operating Systems
Midterm review:
– closed book
– multiple choice
– chapters 1 to 9
Chapter 1&2: The Basics
• kernel mode or kernel space
• user mode or user space
• system call:
– user mode program invokes kernel mode
functionality
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Chapter 2: Operating System
Architectures
•
•
•
•
monolithic
layered
micro-kernel
distributed
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Chapter 3: Process
end
begin
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Process Control Blocks Execution context
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Context Switch
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Interrupt Processing
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Chapter 4: Thread vs.
Process
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Combining User- and Kernel-level
Threads
m-to-n thread mapping:
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Chapter 5: Concurrent
execution
• System has more than one
thread/process
• either independent or in cooperation:
– mostly independent
– occasionally need to communicate or
synchronize
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Mutual exclusion algorithm
• General structure of process Pi (vs. Pj)
do {
entry protocol
critical section
exit protocol
remainder section
} while (true);
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Semaphore
• Software construct to enforce mutual
exclusion
• Contains a protected variable:
– accessed via wait and signal commands
P
V
• binary semaphore: 0 or one
• counting semaphore
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Chapter 6: Monitor
• Programming language construct
– Contains data and procedures needed to
access shared resource
• resource accessible only within the monitor
• Supports:
– mutual exclusion
– synchronization
• Dijkstra, Brinch-Hansen, Hoare
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Chapter 7: Conditions for Deadlock
• Mutual exclusion
– resource accessed by only one process at a time
• Hold-and-wait-for
– process holds resource(s) while waiting for other
resource(s)
• No-preemption
– system cannot remove resource from the process until
the process has finished using the resource
• Circular-wait
– processes are in a “circular chain” where each process
is waiting for resource(s) of next process in chain
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Chapter 8: Processor
scheduling
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Scheduling Criteria
•
CPU utilization
– keep the CPU as busy as possible
• Throughput
– # of processes that complete per time unit
• Turnaround time
– amount of time to execute a process
• Waiting time
– time a process has been waiting in the ready queue
• Response time
– time from request until first response is produced
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Chapter 9: Memory
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Evolution of memory organization
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Preparation:
• Self review questions
• Chapter exercises
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