Flashcards
SCC 211 - Going Deeper
Cards in this deck (15)
- 1Problem with external fragmentation?Suffer external fragmentation*
– Segmentation (as opposed to paging) just one such scheme
– Also see same problem with non-block based file-systems - 2Different storage allocation methods and describe them?– First fit
• Always allocate first region of sufficient size found
– Best fit
• Always allocate smallest memory hole of sufficient size
– Worst fit
• Always allocate largest memory hole (of sufficient size) - 3Within scheduling multiple processes, what picks the next process?Scheduler picks next process
– Selected process then dispatched to run on CPU - 4State the different scheduling criteria?• CPU Utilisation (max 100%, often given as number 0..1)
Throughput
Turnaround time
Waiting time
Response time - 5What is the CPU utilization time?– Percentage of time CPU running application code
- 6What is the throughput time?– Number of processes completed per unit time (obv. depends on size)
- 7What is the turnaround time?– Time between process submission and completion
- 8What is the waiting time?– Sum of time waiting in Ready Queue (i.e. it could run/ use CPU)
- 9What is the response time?– Time between submission and start of first output/ interaction
- 10State the waiting times formula?Waiting Times (dispatch time – arrival time)
- 11What is the average waiting time?– Average time processes wait in Ready Queue
- 12What is the average turn around time?– Average time between submission and completion
- 13State the turn around time formula?Turnaround Times (completion – arrival time)
- 14What is round robin methodology?• Pre-emptive scheduler with set time quantum
- 15State the two simple algorithms for page replacement?– First In, First Out (FIFO)
• Simple but can exhibit unexpected behaviour *
– Least Recently Used (LRU)
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- Flashcards on SCC 211 - Going Deeper, created by Ayo Olutobi on 21/04/2017.
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- Ayo Olutobi
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