537 First Half Exam Review Newest Update

537 First Half Exam Review Newest Update

A proportional share / fair share scheduler: instead of optimizing for
___________________________, the scheduler might instead try to guarantee that
________________________________________. - ANS-turnaround or response time,
each job obtains a certain percentage of CPU time
Lottery scheduling is ______________, not _______________________ - ANSprobabilistic, not deterministic
High level outline of lottery scheduling? - ANS-- scheduler knows how many total tickets
there are
- divide total tickets among the processes
- for each time slice, scheduler picks a winning ticket (which is within the range of all
tickets), and then the scheduler loads the context of the winning process.
3 advantages of using randomness for lottery? - ANS-- avoids strange corner cases
which more traditional algorithms might have (say LRU)
- random is lightweight, and requires very little state information
- random is pretty fast
_____________________ are often useful for modeling representing proportions of
ownership - ANS-tickets
______________________________ can be used to let users allocate tickets on any
scale they like, and have all of these scales converted to a single global one by the
system.
______________________ allows a process to temporarily hand off its tickets to
another process (esp. useful for a client/server setting)
________________________, given that processes trust each other, is when a process
can temporarily raise/lower the # tickets it owns, to reflect needed CPU time without
communicating with other processes - ANS-ticket currency
ticket transfer
ticket inflation
What is the Unfairness metric (U) defined to be?
A perfectly fair scheduler would achieve U = ______ - ANS-time first job completes /
time second job completes