General Rules

• This is a 24h take-home exam.
• The exam runs from 17:00 on Monday, 20 November 2000 to 17:00 on Tuesday, 21 November 2000
• The basic exam question is available now, but the papers you are asked to analyse will be made available only at 17:00 on Monday, 20 November 2000.
• The papers will be available in hardcopy from my office and electronically via this WWW page.
• The total exam is worth 35 marks.
• You will lose 3.5 marks for each hour, or part thereof, your submission is late.
• You are not to get any help from anyone on the exam. You should not talk to anyone else about the exam from the time you receive the full details until you submit your solution.
• You have the choice of three different ways to submit your solution:
  1. Submit a hardcopy by the deadline (17:00 on Tuesday, 21 November 2000). It must be accompanied by the signed certification of sole authorship.
  2. Submit an electronic copy, via the give system, by the deadline, and submit a hardcopy, including the signed certification of sole authorship, not more than three days later. In this case the electronic copy must be a PostScript or PDF file, which, when printed on a CSE printer, appears identically to the submitted hardcopy. The submission must have a file extension .ps or .pdf.
     The electronic copy must be submitted via the``give'' system, mark name ``exam''.
  3. Submit, by the deadline,
  a digitally signed electronic copy. This must contain your full name, student number, date, and the following declaration:

  I hereby declare that this submission is my own work, and I have not received any help whatsoever.

  The file must be signed with PGP, be ASCII, and have an extension .pdf.asc or .ps.asc. This is achieved (when using PGP 5.0 or later) with the command:

  pgps -a <file>

  The extracted PostScript or PDF file must print on a CSE printer.
  The electronic copy must be submitted via the``give'' system, mark name ``exam''.

Notes on digitally signed submissions

1. Familiarise yourself with PGP (or GPG). We will not provide tutorials on this, it's up to you. Get yourself a public key if you don't have one. Follow the recommended safeguards to keep it secure. It will be like your normal signature!
2. See Alan to have him sign your key. This requires that you supply appropriate proof of identity (student card, if the picture isn't clear enough we may require further identity proof).
3. See me, with your key signed by Alan, and proof of identity. I will then sign your key.
4. This doubly-signed key can then be used to sign your exam. (Feel free to get others to sign your key as well.)
5. Make sure that PGP or GPG is installed on the system you are going to use to write your exam, and that you can use it reliably. If you stuff up it's your own problem.

Specifics

• Paper 1: Chiueh et al, SOSP '99   PostScript   PDF
• Paper 2: Kim et al, OSDI '00   PostScript   PDF (BIG!)

You are to read, understand, and critically assess the papers. Questions you may want to ask yourself for each of the papers:

• What problem is it trying to address
• How well does it address the issue
• How does it relate to other work? Does it reference relevant other work (as far as you can tell), does it do the other work justice?
• How technically sound is it? Does their argumentation, the presented data convince you? Should they have been looking at other issues?
• How good are the results?
• How good/deep is their analysis?
• How easy would it be to reproduce their results?
• How general are their results? Can they be applied to other systems? Did we learn some general truth?
These are only hints, I am not asking you to explicitly answer all these for each paper. However, you may find those questions helpful in critically analysing the papers. Imagine you are a reviewer for a conference to which the papers have been submitted, and you are to judge their contribution to the field.

Note that all papers are in fact published (and therefore cannot be all that bad :-)

Here are (very good) sample solutions, which were done in ``real-time'' by one of the students taking the exam:

• Sample report on Chiueh et al.
  Other points the author could have made:
  • user-level extensions are not protected from each other, nor from the base code,
  • the scheme does not allow extending extensions,
  • time protection relies on an arbitrary global timeout value,
  • it is not clear how this scheme maintains protection if processes are multithreaded (and one can suspect it doesn't),
  • the paper uses meaningless digits (e.g., 15.22 when they say themselves that the standard deviation is 2%).
• Sample report on Kim et al
  Other points the author could have made:
  • tuning of other schemes (rather than using their authors' "recommended values") might have improved their performance,
  • they could have done some runs showing that the automatically chosen steady-state partitioning of the buffers performs indeed best,
  • they should have commented on the (apparently?) sequential accesses in the "other" graph of Fig 7b,
  • their CPU-bound benchmark only gives a worst case value for their overheads (so they could actually be lower),
  • they could have commented on how reasonable it is to base their definition of sequential access on access in increasing logical block order.
Note: this is an exam, not betting on horses. It is dangerous to guess what I might think of the paper, or to guess that there'll be a good and a bad one. Papers are selected on other criteria.

What to submit

You are to submit a report which summarises for each paper the basic ideas behind their work. You are to give a critique of the technical merits, achievements and shortcomings (if any). The papers are not directly related, so you don't have to compare them (although feel free to do a comparative analysis if you think it makes sense).

I am intentionally not specifying a length limit. However, I strongly encourage you to be concise. Lengthy submissions will almost certainly be unfocussed and waffly. I cannot imagine a decent job in excess of 3000 words, and would imagine that a very good submission would stay well below 2000 words total. If your report gets longer than this you should step back and try to focus.

What I will be looking for

You will be marked on the level of understanding and critical analysis portrayed in you submission. All relative to what can be reasonably expected from you (I know that none of you have a PhD in OS yet :-)

1999 exam

You may find it useful to look at last year's exam, and the sample reports provided there.

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COMP9242, School of Computer Science and Engineering, University of New South Wales

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