Description
In this project you will learn how to create threads in Nachos. You are given a simple thread system
for Nachos. Your tasks are:
1. Compile Nachos and run the system.
2. Add some lines to the Nachos code. Recompile and run it.
3. Add several specified lines in the Nachos code. Recompile and run it.
4. Save the output and explain the results.
Don’t be overwhelmed by the sheer amount of code provided. In fact you don’t need to care about
most of it. The part that you need to read or modify will be given in this instruction.
Task 1: Running Nachos with pre-implemented semaphore
Step 1: download Nachos source code, with pre-implemented semaphore.
wget http://course.cse.ust.hk/comp3511/project/project1/os_nachos_proj1.tar.gz
Step 2: Extract the source code.
tar -zxvf os_nachos_proj1.tar.gz
Step 3: Compile the code
Enter the folder “os_nachos_ proj1” and then run “make”
Step 4: Run nachos
In the folder “os_nachos_ proj1”, run “./nachos”
In this program, Nachos creates one thread, which does nothing except telling us its name
“Thread1” and its termination.
If you succeed in running nachos, you will see these messages:
Hello, my name is Thread1
Thread1 ends
No threads ready or runnable, and no pending interrupts.
Assuming the program completed.
Machine halting!
Ticks: total 30, idle 0, system 30, user 0
Disk I/O: reads 0, writes 0
Console I/O: reads 0, writes 0
Paging: faults 0
Network I/O: packets received 0, sent 0
Cleaning up…
Step 5: Save the output to file
./nachos > project1_output1.txt
This command runs Nachos and saves the output to file project1_output1.txt
Keep the file project1_output1.txt for grading.
Task 2: Adding codes to Nachos
Open file os_nachos_ proj1/threads/project1.cc. All the code you need to write is in this file.
There are 4 functions in the file. running_for_calculation(), latter_thread(), prior_thread() and
project1(). Do NOT modify the function running_for_calculation().
Your work is to add your code in function latter_thread(), prior_thread() and
project1(). Nachos will automatically invoke project1(). Your tasks are:
Step 1:
In Thread1 (i.e. function prior_thread() ), invoke function running_for_calculation() to perform
certain number of calculations specified by the parameter “arg” . Before the function
running_for_calculation() is invoked, output the information which claims that Thread1 will
perform calculation for “arg” * 10000 times.
Step 2:
Create second thread called Thread2. This thread invokes function latter_thread ().
Step 3:
In Thread2 (i.e. function latter_thread() ), invoke function running_for_calculation() to perform
certain number of calculations specified by the parameter “arg” . Before the function
running_for_calculation() is invoked, output the information which claims that Thread2 will
perform calculation for “arg” * 10000 times.
Step 4:
Add two code lines in Thread1 (i.e. function prior_thread(), under Task-Comment 1 ) and
Thread2 (i.e. function latter_thread(), under Task-Comment 7 ) to get the priority of the
current thread and output it. Please read the source file thread.h and thread.cc to find the
proper function to get the priority of current thread.
Don’t know what to do? Here are some instructions that may be helpful.
1. How to create threads in Nachos?
First, you need to define a Thread object, then invoke Fork():
Thread *th1 = new Thread(“Thread1”);
th1->Fork(prior_thread, 6);
A thread named “Thread1” will be created, and it invokes prior_thread as its working thread
function. The working thread function must have a parameter of int type. e.g. prior_thread()
function has a “int arg” parameter. The second line invokes the working thread function and
passes the value 6 to the parameter.
Note: Do NOT define the object like “Thread th1(“Thread1″)”. This will cause Nachos to crash.
2. How to get the name of a thread in Nachos?
currentThread->getName();
This function returns the name (pointer of char *) of current thread.
3. About running_for_calculation(int t) function
This function is provided to you. Do NOT modify it. This function will perform the calculation of
addition for certain times specified by parameter t. When the calculation is completed, current
thread invokes Yield() function to relinquish the CPU if any other thread is ready to run. If so,
current thread is put at the end of the ready list, so that it will then eventually be re-scheduled.
4. About latter_thread(int arg) function
This function will make Thread2 invoking running_for_calculation() function as Thread1 did
previously.
Step 5:
After you finish coding in Step 2, re-run “make” and “./nachos”. Your output should be:
Hello, my name is Thread1
my priority is 10
Thread1 will perform calculation for 60000 times
Hello, my name is Thread2
my priority is 10
Thread2 will perform caculation for 70000 times
Thread1 ends
Thread2 ends
No threads ready or runnable, and no pending interrupts.
Assuming the program completed.
Machine halting!
Ticks: total 70, idle 0, system 70, user 0
Disk I/O: reads 0, writes 0
Console I/O: reads 0, writes 0
Paging: faults 0
Network I/O: packets received 0, sent 0
Cleaning up…
Your output is not necessary to be the same but 3 points must be satisfied:
1. Print the name and priority of Thread1 and Thread2.
2. Print the information claiming that thread1 is going to perform calculation for certain times
with the right parameter.
3. Thread1 ends before Thread2
Step 5: Save the output to file
./nachos > project1_output2.txt
This command runs the Nachos and save the output to file project1_output2.txt
Keep project1_output2.txt for grading.
Task 3: Simple Thread Scheduling in Nachos
In this task, you are asked to fulfill the following 8 steps.
Step 1: Add four code lines in source file project1.cc
Add two code lines under Task-Comment 5 (within the function latter_thread()) and TaskComment 12 (within the function prior_thread()) for printing the global variable “global”
information in the two threads and the printed message should claim the thread name where
the global variable is. For example, the printed message should be in a format like:
The global variable in Thread1 is 1
Then, please add the code line
th1->Suspend();
under Task-Comment 2 of the source file project1.cc (within the function latter_thread()). Please
do NOT delete the comment line.
Add the code line
th1->Resume();
under Task-Comment 6 of the source file project1.cc (within the function latter_thread()). Please
do NOT delete the comment line.
Step 2: Rebuild the project and re-run “nachos”
Enter the project1 folder and run “make” again to rebuild the project. Make sure the
building process is without errors or you should revise the code and get rid of them. When you
run “./nachos”, your output should be:
Hello, my name is Thread1
my priority is 10
Thread1 will perform calculation for 60000 times
Hello, my name is Thread2
my priority is 10
Student’s suspend routine called
Thread2 will perform calculation for 70000 times
The global variable in Thread2 is 5
Thread2 ends
The global variable in Thread1 is 8
Thread1 ends
No threads ready or runnable, and no pending interrupts.
Assuming the program completed.
Machine halting!
Ticks: total 90, idle 0, system 90, user 0
Disk I/O: reads 0, writes 0
Console I/O: reads 0, writes 0
Paging: faults 0
Network I/O: packets received 0, sent 0
Cleaning up…
Step 3: Save the output to file
Right after the previous step, please run command
./nachos > project1_output3.txt
which saves output of the modified “nachos” to project1_output3.txt.
Step 4: Scheduling the two threads in a different order
Please comment out your comment under Task-comment 2 and Task-Comment 6, and then add
two code lines to proper position of prior_thread() for scheduling the two threads in a different
order comparing to Step 1.
Step 5: Rebuild the project and save the output to file
Enter the project1 folder and run “make” again to rebuild the project. Please run command
./nachos > project1_output4.txt
which saves output of the modified “nachos” to project1_output4.txt.
Step 6: Scheduling the two threads with an additional command line
Please comment out your comment under Task-comment 8 and Task-Comment 13.
Then, please add the code line
currentThread->Yield();
under Task-Comment 11 of the source file project1.cc (within the function prior_thread ()).
Please do NOT delete the comment line.
Step 7: Rebuild the project and save the output to file
Enter the project1 folder and run “make” again to rebuild the project. Please run command
./nachos > project1_output5.txt
which saves output of the modified “nachos” to project1_output5.txt.
Step 8: Compare the outputs of task 3
Find out the difference among the outputs of task 3 which are saved in
project1_output3.txt, project1_output4.txt and project1_output5.txt, respectively. Describe and
explain the difference briefly. You are required to write the answer in project1_report.txt.
Note: Keep project1.cc, project1_output3.txt, project1_output4.txt , project1_output5.txt and
project1_report.txt for grading.
After you finish these tasks:
1) Please generate a single file using ZIP and submit it through CASS.
2) The name of the ZIP should be “proj1_********.zip”, using your student ID to
replace star symbols.
3) The following files should be included insides the ZIP:
File Name Description
project1.cc Source file you have accomplished by the end of Task 3
project1_output1.txt Output of Task 1
project1_output2.txt Output of Task 2
project1_output3.txt The first output of Task 3
project1_output4.txt The second output of Task 3
project1_output5.txt The third output of Task 3
project1_report.txt The answer to the question in Step 6 of Task 3
