1. Nachos Project Assignment 2 CPU scheduling

2. If you still have trouble to install Nachos
decstation.linux-xgcc.gz

3. Part 1-System call 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

4. System call:start.s
Assembly language assist to make system calls to the Nachos kernel
Take System call Sleep as an example
.globl Sleep
.ent Sleep
PrintInt:
addiu $2,$0,SC_Sleep
// put system call number in register 2
syscall
/* all parameter of this system call will be stored in register4, 5, 6, and 7 by MIPS machine automatically. */
.end PrintInt

5. Part 2-Non-preemptive shortest job first scheduler
Nachos default scheduler: Round Robin
Shortest job first
n+1 = tn + (1- )n
n time of the nth predicate CPU burst
tn time of the nth actual CPU burst
Design several test case to proof your result
your code and presentation files(report) to TA

6. Non-preemptive shortest job first scheduler
thread/alarm.cc, thread/alarm.h
Implement WaitUntil(int x) to handle sleep(int t)
Add a class to management the threads which are sleeping
Begin Running
Invoke Sleep(x)
Per timer interrupt:
1.Record actual CPU burst
2.Wake up time up threads
1.Set next predicted CPU burst
2.Insert this thread to Sleeping thread lists
3.Invoke thread->Sleep

7. More details
system-call.html