Summarizing Scheduling Policies – Georgia Tech – Advanced Operating Systems

Summarizing Scheduling Policies – Georgia Tech – Advanced Operating Systems


So to summarize the scheduling policies, I already mentioned that first come first serve simply ignores affinity, and pays attention only to fairness. And these next two policies that I introduced to you, fixed processor and last processor, the focus is on cache affinity of a thread with respect to a particular processor. That’s what we’re focusing on. And Fixed Processor was the last processor. The next two policies, they focus not only on cache affinity, but also cache pollution. In particular it asks the question, how polluted is a cache going to be by the time Ti gets to run on the processor. That’s the question we’re asking (no period) In both minimum intervening, as well as minimum intervening plus queuing, in terms of making a scheduling decision. And that should be clear, from the discussion up until now, the amount of information that the scheduler has to keep. Grows as you grow, go down this list. The order of arrival is all that you care about, you put them in priority order in the queue and you’re done with it. And you have, the schedule has to do a little bit more work, in each one of these cases, and corresponding with the amount of information that this schedule has to keep for every one of these scheduling policies is going to be more. But the result of scheduling decision is likely to be better when you have more information to make the scheduling decision. Another way to think about the scheduling policy is that, the fixed processor and the last processor is thread-centric in saying what is the best decision for a particular thread with respect to it’s execution. Where does this MI and minimum intervening plus queuing? Both of these are processor-centric, saying that, what thread should a particular processor choose in order to maximize the chance that the amount of cache contents is going to be relevant for the currently scheduled thread? So that’s what we’re looking at. Now that I’ve introduced to you these scheduling policies, it’s time for a quiz.