CSE 120 Midterm Review: Operating Systems Concepts - Prof. Geoffrey M. Voelker, Study notes of Computer Science

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        Midterm Review Geoffrey M. Voelker October 25, 2000 CSE 120 – Midterm Review 2   
The midterm
Architectural support for OSes
OS modules, interfaces, and structures
Processes
Threads
Synchronization
Scheduling 2 October 25, 2000 CSE 120 – Midterm Review 3   
Covers material through scheduling
Based upon lecture material, homeworks, and project
Open book, open notes
Please, do not cheat  Do not copy from your neighbor.  I will notice  No one involved will be happy, including me October 25, 2000 CSE 120 – Midterm Review 4     
Types of architecture support  Manipulating privileged machine state  Generating and handling events 5 October 25, 2000 CSE 120 – Midterm Review 9   
How are the components organized?  Monolithic kernels  Layering  Microkernels
What are the advantages and disadvantages of each? October 25, 2000 CSE 120 – Midterm Review 10   
What is a process?
What resource does it virtualize?
What is the difference between a process and a program?
What is contained in a process? 6 October 25, 2000 CSE 120 – Midterm Review 11   #  
Process Control Blocks (PCBs)  What information does it contain?  How is it used in a context switch?
State queues  What are process states?  What is the process state graph?  When does a process change state?  How does the OS use queues to keep track of processes? October 25, 2000 CSE 120 – Midterm Review 12     
What does CreateProcess on NT do?
What does fork() on Unix do?  What does it mean for it to “return twice”?
What does exec() on Unix do?  How is it different from fork?
How are fork and exec used to implement shells? 7 October 25, 2000 CSE 120 – Midterm Review 13 $ 
What is a thread?  What is the difference between a thread and a process?  How are they related?
Why are threads useful?
What is the difference between user-level and kernel- level threads?  What are the advantages/disadvantages of one over another? October 25, 2000 CSE 120 – Midterm Review 14 $ !   
How are threads managed by the run-time system?  Thread control blocks, thread queues  How is this different from process management?
What operations do threads support?  Fork, yield, sleep, etc.  What does thread yield do?
What is a context switch?
What is the difference between non-preemptive scheduling and preemptive thread scheduling?  Voluntary and involuntary context switches 10 October 25, 2000 CSE 120 – Midterm Review 19   
What is a monitor?  Shared data  Procedures  Synchronization
In what way does a monitor provide mutual exclusion?  To what extent is it provided?
How does a monitor differ from a semaphore?
How does a monitor differ from a lock?
What kind of support do monitors require?  Language, run-time support October 25, 2000 CSE 120 – Midterm Review 20
    ) *
What is a condition variable used for?  Coordinating the execution of threads  Not mutual exclusion
Operations  What are the semantics of Wait?  What are the semantics of Signal?  What are the semantics of Broadcast?
How are condition variables different from semaphores? 11 October 25, 2000 CSE 120 – Midterm Review 21 !     
What does the implementation of a monitor look like?  Shared data  Procedures  A lock for mutual exclusion to procedures (w/ a queue)  Queues for the condition variables
What is the difference between Hoare and Mesa monitors?  Semantics of signal (whether the woken up waiter gets to run immediately or not)  What are their tradeoffs? October 25, 2000 CSE 120 – Midterm Review 22 ' ( 
    ) 
In Nachos, we don’t have monitors
But we want to be able to use condition variables
So we isolate condition variables and make them independent (not associated with a monitor)
Instead, we have to associate them with a lock (mutex)
Now, to use a condition variable…  Threads must first acquire the lock (mutex)  CV::Wait releases the lock before blocking, acquires it after waking up 12 October 25, 2000 CSE 120 – Midterm Review 23    
What kinds of scheduling is there?  Long-term scheduling  Short-term scheduling
Components  Scheduler (dispatcher)
When does scheduling happen?  Job changes state (e.g., waiting to running)  Interrupt, exception  Job creation, termination October 25, 2000 CSE 120 – Midterm Review 24    +
Goals  Maximize CPU utilization  Maximize job throughput  Minimize turnaround time  Minimize waiting time  Minimize response time
What is the goal of a batch system?
What is the goal of an interactive system?