ECS-251, Winter 2009, Programming Assignment #1
Due date: the interactive grading appointment around 01/23/2009
Total 10%
Lottery Scheduling in the FreeBSD 5.x Kernel
This assignment is related the “lottery scheduling” algorithm in FreeBSD 5.4 kernel.
Please make sure that you follow a good coding convention. You need to provide a
Makefile and a README.txt. And, most importantly, you will need to develop some test
programs to demonstrate the effects of lottery scheduling.
Modify the FreeBSD 5.x kernel such that the users can give different amount of lottery
tickets to each “user” process. Please note that you do not need to worry about “lottery
ticket sharing” case – just the simplest form of lottery scheduling. We still maintain
different levels of priorities as in FreeBSD, but you need to implement TWO different
options:
(1). The lottery mechanism will be placed ONLY in the real-time and time-sharing
scheduling class (i.e., priorities 128~223).
(2). The lottery mechanism will be placed also in higher scheduling classes (i.e., priorities
0~223). In other words, you need to give kernel classes more tickets to start with such as
128 (lower kernel), 32 (high kernel), 8 (real-time), 4 (time-share), 1 (otherwise).
You will need to add one new attribute “ int tickets” into “struct proc”
defined in “/usr/src/sys/sys/proc.h”, and one global variable “int
lottery_mode” in “/usr/src/sys/kern/kern_switch.c”. And, you will
need to add the following four system calls:
int setProcessTickets(int pid, int tickets);
int getProcessTickets(int pid);
int setLotteryMode(int mode);
int getLotteryMode(void);
First, by default, each user process in the time-sharing class has four tickets, while a user
program can set the ticket number differently using the setProcessTickets system
call. Second, your kernel use “normal BSD scheduling” by default, and the amount of
tickets in each process makes no impact to the scheduling behavior. However, when a
user process sets the lottery_mode to 1 (via the setLotteryMode system call),
the kernel changes its scheduling behavior immediately to “lottery scheduling”.
The original Lottery Scheduling can be found at:
http://www.usenix.org/publications/library/proceedings/osdi/full_papers/waldspurger.pdf
Your team will need to write a couple test programs to test whether your implementation
distributes CPU cycles to the process according to the lottery scheduling principle.
