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

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

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

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

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

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

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

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