Wow. I actually made it. Since early-ish at CMU, I had known that an “OS TA” was a laudable thing to be¹, but after The OS Semester, I wasn’t sure I’d actually be one. Sure, I’d applied the semester I was already scheduled to be a TA for 15-316, and applied again “just in case”, but I didn’t really think I’d actually get it. It was only (checks notes) December 24th that I found out for sure, through a friend refreshing the TA assignment page for their own position. What a Christmas present lol.

This final semester at CMU, I only took 15-462 Computer Graphics, so I had plenty of time to attend another class, do research for a professor, teach my stuco, and TA this class. hm. work expands to fill the available time, huh?

What Does An OS TA Do?

In a nutshell:

• grade projects
• hold office hours
• slowly add to existing projects

All in collaboration with Professor Dave Eckhardt, who has been teaching the course for long enough to have taught some current professors at CMU.

Oh! Also! I was the only “official” TA that semester, all others were alumni or PhD students kindly contributing in their spare time.

Grading

This is The Big One™. All 5 projects, 2 homeworks, a midterm, and a final.

For those latter 3 categories of written assignment, it’s not too big a deal. There are fairly standardized rubrics/methodologies for grading, and the main feedback given is point values (which students can come into office hours to discuss if they want). What makes OS grading so infamous² for its grading is the sheer amount of extremely detailed feedback given on all the coding projects.

For those coding projects, there is a standard set of tests that the code has to pass³, and then the rest of the points are left to Architecture and Code Quality. How do you grade these? You read the code, of course! And by “you” I mean “me and Dave and a small army of masters/PhD students/alumni”.

Reading all the code written by other students (especially by masters students!) was really useful. It made me appreciate my own coding style⁴ also opened my eyes to other things you should pay attention to while coding.

I will be part of the “small army” next semester⁵, and will be more than happy to help read more code :)

Office Hours

As the only “official” TA, I did hold a lot of office hours. Dave (Eckhardt) and Dave (O’Halloran) also held their own professor office hours, and a few alumni held remote office hours on weekends.

In office hours, I was supposed to never give out solutions, only ask questions about what they had tried and hadn’t tried in an attempt to get them to think about the problem more fully. This method is difficult and frustrating on both sides but on the whole I agree that it does lead to better learning outcomes.

I stuck to a fairly regular schedule and was always surprised by when students did or didn’t come in. There were sometimes big influxes after an assignment was released, right before it was due, or even just in the middle, but just as often those times would be empty. And I would work on grading during the downtime instead (:

Adding To Existing Projects

Due to a limit on the number of hours I could work in a week⁶, and a general sense of wanting to do other things besides OS, I unfortunately did not do a whole lot of this. I tried my best at updating the VM infrastructure to the now-publicly available version instead of the older still-proprietary one CMU uses, and failed due to some very interesting reasons that I should probably write up some time.

I was able to write a small test program for P4 that ran on a hypervisor that the students wrote, but really Dave did most of the tough stuff with super funky cursed Assembly and I just had to understand why it worked and hook it up into a small shell. It is called dog and when you type “dog” it types out “cat” instead, wow crazy.

Did I Enjoy It?

I think this was a very worthwhile experience! I highly respect Dave Eckhardt so having more time to interact with him was fun. There were also some fun parts to grading and office hours, but on the whole it was a lot of work. I still would do it again though. Even if it feels like a slog during, I can come out the other side feeling like “yeah, I Did That”. Just like taking OS, I guess.