Description
In this lab you will make minor modifications and minor additions to the source code for the teaching
operating system Pintos.
Specifically, you will implement a more efficient version of the Pintos system call timer_sleep found in
src/devices/timer.c in the Pintos distribution supplied for this lab.
This lab is worth 5% of your final grade.
CMPS 111 Lab 1
Setup
SSH in to one of the two CMPS111 teaching servers using your CruzID Blue password:
$ ssh @noggin.soe.ucsc.edu ( use Putty http://www.putty.org/ if on Windows )
Or $ ssh @nogbad.soe.ucsc.edu
Authenticate with Kerberos:
$ kinit @CATS.UCSC.EDU
Authenticate with AFS:
$ aklog
Create a suitable place to work: ( only do this the first time you log in )
$ mkdir –p CMPS111/Lab1
$ cd CMPS111/Lab1
Install the lab environment: ( only do this once )
$ tar xvf /var/classes/CMPS111/Spring18/Lab1.tar.gz
Build Pintos:
$ cd ~/CMPS111/Lab1/pintos/src/threads ( always work in this directory )
$ make
Also try:
$ make check ( runs the required functional tests – see below )
$ make grade ( tells you what grade you will get – see below )
Additional Information
void timer_sleep(int64_t ticks) should suspend execution of the calling thread until time has
advanced by at least the requested number of ticks. Unless the system is otherwise idle, the thread need not
wake up after exactly ticks. It is entirely valid to just put it on the ready queue after they have waited for the
right number of ticks.
The ticks argument is expressed in timer ticks, not in milliseconds or any other unit. Do not change this
data type unless you want lots of the tests to fail.
Separate functions timer_msleep, timer_usleep, and timer_nsleep exist for sleeping a specific
number of milliseconds, microseconds, and nanoseconds respectively, but these will call timer_sleep as
appropriate. You do not need to modify them.
CMPS111 Lab 1
Accessing the teaching servers file systems from your personal computer
You home directories on the teaching servers are UCSC AFS, i.e. they are the same as if you logged into
the UCSC Unix Timeshare. To access files in your home directory to edit them using an IDE on your laptop,
you can do one of two things:
• Use an SSH synchronization client like Cyberduck: https://cyberduck.io/
o Configure Cyberduck to point at either of the teaching servers
o Connect with your CruzID and Blue Password
• Install an AFS client on your laptop: https://www.auristor.com/openafs/client-installer/
o The Kerberos realm is: CATS.UCSC.EDU
o The OpenAFS Cell is: cats.ucsc.edu
o Use your CruzID and Blue Password
o This is a far from trivial setup. If you get stuck, switch to using something like Cyberduck.
o DO NOT CONTACT UCSC AFS SUPPORT FOR ANY REASON WHATSOEVER
CMPS 111 Lab 1
Requirements
Basic:
• You have modified the implementation of void timer_sleep(int64_t ticks) function found
in src/devices/timer.c
• Your modified implementation passes the following functional tests:
o alarm-single
o alarm-multiple
o alarm-simultaneous
o alarm-zero
o alarm-negative
• Your implementation is demonstrably efficient (a non-functional test).
What steps should I take to tackle this?
Come to the sections and ask.
How much code will I need to write?
A model solution that satisfies all requirements adds approximately 20 lines of executable code.
Grading scheme
The following aspects will be assessed:
1. (100%) Does it work?
a. Tests pass [5% per test] (25%)
b. Your implementation is demonstrably more efficient than the original (75%)
2. (-100%) Did you give credit where credit is due?
a. Your submission is found to contain code segments copied from on-line resources and you
failed to give clear and unambiguous credit to the original author(s) in your source code (-100%)
b. Your submission is determined to be a copy of another past or current CMPS111 student’s
submission (-100%)
CMPS111 Lab 1
What to submit
In a command prompt:
$ cd ~/CMPS111/Lab1/pintos/src/threads
$ make submit
This creates a gzipped tar archive named CMPS111-Lab1.tar.gz in your home directory.
UPLOAD THIS FILE TO THE APPROPRIATE CANVAS ASSIGNMENT.
Looking ahead
Subsequent labs will require a short report and will have additional assessment criteria, including:
Is it well written?
Marks awarded for:
• Compilation free of errors and/or warnings.
• Clarity
• Modularity
Marks deducted for:
• Failing to do any of the above
• Not following C language good practice (e.g. don’t use magic numbers)
I strongly recommend you consider these issues in this lab to get some practice in.
CMPS111 Lab 1
