Part 1 - System call

System Call (Cont.)

Implement a system call - Sleep()

• userprog/syscall.h
  • Define a system call number of Sleep
• test/start.s
  • Prepare registers for Sleep
• userprog/exception.cc
  • Add a new case for Sleep in ExceptionHandler
  • Note the use of kernel->alarm->WaitUntil()

System Call (Cont.)

• Alarm - software alarm clock, that generates an interrupt every X time ticks
  • threads/alarm.h
• The WaitUntil() will be called when a thread going to sleep.
• Call the CallBack() to check which thread should wake up.
• See the comments in the file, they are helpful.
• Don’t forget the useful data structure like list in the lib folder.

System Call (Cont.)

• Write your own test code like test1 and test2
  • Create test.c in test/
  • Modify the Makefile in test/
  • Compile in the same way as test1 and test2

Part 2 - CPU Scheduling

RR, FCFS, SJF, Priority

CPU Scheduling

Choose at least one of the following to implement (The extra implementation will be considered as BONUS) :

• First-Come-First-Service (FCFS)
• Shortest-Job-First (SJF)
• Priority

Design your own test code :

• Modify Thread::SelfTest() or create your method for testing.

CPU Scheduling (Cont.)

Design at least 2 test cases to proof your result

• Specify your algorithm in the report.
• Specify the test case setting and output in your report.
• Design the NachOS interface to switch different scheduling algorithm
  • threads/main.cc

Reference

• The University of Chicago - Com Sci 230 System Calls and Other Exceptions
• Purdue University - CS 354 Thread Scheduling and Sleeping

Report & Policy

Report contents, grading policy, late policy

Report

1. Motivation
   • Motivation and the problem analysis
   • What’s your plan to deal with the problem
2. Implementation
   • How do you implement to solve the problem in Nachos
   • You can including some (not all) important code segments and comments
3. Result
   • Experiment result and some discussion
   • Extra effort or observation

Grading Policy

• Nachos source code: (40%)
• Report: (40%)
• Correct format: (20%)
• No plagiarism

Late Policy

• 10% penalty per day
• After 7 days, you will get 70% penalty, but no more penalty after that.

Submission

Create a folder for the source code and report

{Student ID}_Nachos2/
  |_ nachos-4.0/
  |_ report.pdf

// Name the folder w/o curly braces, e.g. r07943154_Nachos2

Compress

tar -zcvf {Student ID}_Nachos2.tar.gz ./{Student ID}_Nachos2

Your source code and report should be handed out by Ceiba

tags: Fall 2020 OS