1. Midterm Review Chris Gill CSE 422S - Operating Systems Organization
Washington University in St. Louis
St. Louis, MO 63130

2. CSE 522S – Advanced Operating Systems
Midterm Exam
8-10 questions, which will test for comprehension, some key terms and details, and a bit of analysis
Studios are useful for analysis & concepts (and familiarity)
Details from slides & readings matter as well
You will be allowed one 8.5 inch by 11 inch page of notes (with information on one or both sides)
Should be readable with your normally corrected vision
Pens, pencils, erasers, water bottles also allowed
No other materials or sources of information (phones off)
80 minutes total, 8:40-10am on Wed Oct 11
Try to arrive early, in Jolley Hall 309 conference room
Will distribute exams, start promptly at 8:40am
CSE 522S – Advanced Operating Systems

3. CSE 522S – Advanced Operating Systems
Core Concepts
Kernel execution:
Timing:
System calls
Time sources (clocks)
Interrupt handlers
Timers
Kernel threads
Timer granularity
Benchmarking
Kernel programming:
Tracing:
Kernel modules
Core kernel image
Kernel tracing
System call tracing
CSE 522S – Advanced Operating Systems

4. CSE 522S – Advanced Operating Systems
Core Concepts
Processes:
Interrupt handling:
Process creation
Interrupt context
Process address space
Process context
Process family tree
Top half processing
Bottom half processing
Scheduling:
IRQs
O(1) Scheduler
Tasklets
CFS Scheduler
Work queues
Real-Time Scheduler
Scheduler tensions
CSE 522S – Advanced Operating Systems

5. CSE 522S – Advanced Operating Systems
Example Question #1
Imagine you are implementing a new OS feature that communicates with user space. User programs request an action from the kernel, and the kernel returns some data. Consider two options for implementing this feature: syscall vs. kernel module. Give two advantages of implementing this by creating a new system call (4 points): Give two advantages of implementing this by creating a new kernel module that reads and writes files (4 points): If you use the kernel module approach, what must user programs do to pass requests to it after it has been loaded (2 points)?
CSE 522S – Advanced Operating Systems

6. CSE 522S – Advanced Operating Systems
Example Question #2
You have a periodic system where the Linux real-time scheduler runs every ms, the round-robin scheduling interval is 100ms, and there are five tasks, which will consume 300ms, 300ms, 400ms, 500ms, and 700ms of processor time respectively each time they run. If your system schedules tasks in FIFO order on a single core, what is the longest a task might wait before it runs (3 points)? If it instead schedules tasks in round-robin order on a single core, what is the longest a task might wait before it runs (3 points)? Rank the round-robin and FIFO schedulers as as either “HIGH” or “LOW” for each of: response time, overhead, fairness (3 points).
CSE 522S – Advanced Operating Systems

7. CSE 522S – Advanced Operating Systems
Example Question #3
In the blank next to each term below, please write the letter for the text that best matches it and that it best matches (4 points). ___ task structure a. Non-root node of process family tree ___ init process b. Implements process family tree node ___ child process c. Extends process family tree ___ fork call d. Root of the process family tree
CSE 522S – Advanced Operating Systems

8. CSE 522S – Advanced Operating Systems
Midterm Exam
8-10 questions, which will test for comprehension, some key terms and details, and a bit of analysis
Studios are useful for analysis & concepts (and familiarity)
Details from slides & readings matter as well
You will be allowed one 8.5 inch by 11 inch page of notes (with information on one or both sides)
Should be readable with your normally corrected vision
Pens, pencils, erasers, water bottles also allowed
No other materials or sources of information (phones off)
80 minutes total, 8:40-10am on Wed Oct 11
Try to arrive early, in Jolley Hall 309 conference room
Will distribute exams, start promptly at 8:40am
CSE 522S – Advanced Operating Systems