Operating Systems

================ Start Lecture #9 ================
  1. The department wants to know how you feel about recitations as they are again considering having recitations next year for 202 (and possibly other courses as well).
  2. Lab 2, is assigned and is due in two weeks (1 March 2005).
  3. Remember that lab 2, must be done in C (or C++).
End of Notes

Homework: Redo the previous homework for q=2 with the following change. After process P1 runs for 3ms (milliseconds), it blocks for 2ms. P1 never blocks again. P2 never blocks. After P3 runs for 1 ms it blocks for 1ms. Remind me to answer this one in class next lecture.

Processor Sharing (PS, **, PS, PS)

Merge the ready and running states and permit all ready jobs to be run at once. However, the processor slows down so that when n jobs are running at once, each progresses at a speed 1/n as fast as it would if it were running alone.

Homework: 34.

Variants of Round Robin

Priority Scheduling

Each job is assigned a priority (externally, perhaps by charging more for higher priority) and the highest priority ready job is run.

Priority aging

As a job is waiting, raise its priority so eventually it will have the maximum priority.