CS 450 Update Log

If you’re here looking for the current CS 450 website, it’s moved!

The site is now located at http://cs.iit.edu/~lee/cs450

Following is a set of problems that should help you prepare for the v6 portion of the upcoming exam:

• Describe the memory management facilities of the PDP11/40. Specifically, detail the physical/virtual address spaces, and the mapping mechanism used by the MMU.

• What is the resulting memory mapping by the end of line 0669? Does proc 0’s user structure necessarily begin at the beginning of the 6th physical page? Why or why not?

• What is the structure always to be found at virtual address 140000 in the kernel’s address space? What is the significance of this structure, and what must the kernel do with it when switching to a different process?

• What does the stack pointer point to after line 2228 in the first call to swtch, after the kernel booted?

• What data structures are associated with each process in v6? Describe the roles that they play during a process’s lifetime.

• Annotate every line of assembly code for the function _retu, from lines 0740-0749. What does each statement do, and why?

• Explain why the calls to savu and retu are found in the swtch routine at lines 2189, 2193, and 2228. You should describe the processes involved during the function’s execution.

You can download the full text of the Lion’s Commentary on UNIX here, and the sectioned UNIXv6 source code here.

In addition, you may also find this PDP-11 Handbook a handy reference.

I strongly advise you to print this material out and bring it to class if you do not plan on purchasing the dead-tree version. If you do, it’s available on Amazon for much less than most other course textbooks.

Finally managed to wrestle the blog into submission — the assignment below has been updated, and slides are posted. Note the extended due date.

The CPU Scheduling simulator you need for some of the problems in assignment 1 can be found at the UTSA CS Simulators website — look for the “Process (CPU) Scheduling” simulator download. Detailed documentation for the simulator can also be found on the website.

If you like, you can also obtain the simulator via the git version control system by cloning the CS 450 course repository — do this with the following command:

git clone git://github.com/michaelee/cs450.git

Look under the sim/ps directory of the cloned repository.

For those interested in some extracurricular hacking, you can also find a PDP-11 simulator under the sim/simhv directory (courtesy of the Computer History Simulation Project). Compile it with make, and you’ll find the simulator binary at ./bin/pdp11.

Running v6 is then a matter of downloading the software kit, unpacking it, and attaching to it in the simulator and booting up: (I moved the pdp11 binary into the unpacked v6 package directory before starting, below)

foxtrot:uv6swre$ ./pdp11

PDP-11 simulator V3.7-3
sim> set cpu u18
sim> att rk0 unix0_v6_rk.dsk
sim> att rk1 unix1_v6_rk.dsk
sim> att rk2 unix2_v6_rk.dsk
sim> att rk3 unix3_v6_rk.dsk
sim> boot rk0
@unix

login: root
# ls -l
total 182
drwxr-xr-x  2 bin      1040 Jan  1  1970 bin
drwxr-xr-x  2 bin       352 Jan  1  1970 dev
drwxr-xr-x  2 bin       304 Aug 20 12:18 etc
drwxr-xr-x  2 bin       336 Jan  1  1970 lib
drwxr-xr-x 17 bin       272 Jan  1  1970 mnt
drwxr-xr-x  2 bin        32 Jan  1  1970 mnt2
-rw-rw-rw-  1 root    28472 Aug 20 12:01 rkunix
-rwxr-xr-x  1 bin     28636 Aug 20 11:38 rkunix.40
drwxrwxrwx  2 bin       144 Aug 20 12:14 tmp
-rwxr-xr-x  1 bin     28472 Aug 20 12:01 unix
drwxr-xr-x 13 bin       224 Aug 20 12:22 usr
drwxr-xr-x  2 bin        32 Jan  1  1970 usr2

You can find more instructions on the PDP-11 simulator here, and on using the v6 software package here.

In this assignment you’ll try your hand at (manually) simulating a number of scheduling algorithms discussed in lecture. Please type up your submissions and show all your work for full credit — handwritten work will not be accepted! (Diagrams may be neatly hand drawn with a ruler, if you’re not comfortable doing those on a computer).

Submissions are due 6/24/09 at the beginning of lecture. Internet/TV students please have your work submitted via the blackboard digital dropbox by then.

The Process Scheduling Simulator

Consider the following run setup for the scheduling simulator:

seed 5000
numprocs 10
firstarrival 0.0
interarrival constant 0.0
duration constant 50
cpuburst exponential 5
ioburst exponential 10

The following experiment configures the above run with the SJF, preemptive-SJF, and SJFA 0.5 (CPU burst duration predicted using an EMA with a configured alpha of 0.5) algorithms:

run alpharun algorithm SJF key "SJF"
run alpharun algorithm PSJF key "PSJF"
run alpharun algorithm SJFA 0.5 key "SJFA"

Create the necessary configuration files — you may need to add some of your own lines — and run the simulator with the given settings. Refer to the output for exercise 2. Exercises 3 and 4 asks you to make some modifications to the run settings.

cstin 0.5
cstout 0.5