Question

1. Give an example of a Multi-Level Queue with Feedback system. Be sure to fully describe all relevant aspects of the system.
2. Aging is used to solve what problem in process scheduling? Explain how it solves it.
3. What are Hardware Threads? In what way do they impact the Operating System?
4. Regarding Mutex Locks and Semaphores:
   1. A process wishes to unlock a Mutex Lock entitled “EXCLUDE”. What command does it need to issue?
   2. A process requests use of a resource controlled by a Semaphore entitled “PRINTERS”. What command does it need to issue to indicate this?

5. Which of the methods used to map user threads to kernel threads can exploit a multiprocessor environment? Justify your answer.

Answer 1

Example of multiple queue with feedback system

Consider a framework which has a CPU bound cycle, which requires the burst season of 40 seconds.The staggered Feed Back Queue booking calculation is utilized and the queue time quantum '2' seconds and in each level it is augmented by '5' seconds.Then how frequently the cycle will be hindered and on which queue the cycle will end the execution?

Arrangement –

Cycle P needs 40 Seconds for complete execution.

At Queue 1 it is executed for 2 seconds and afterward hindered and moved to queue 2.

At Queue 2 it is executed for 7 seconds and afterward hindered and moved to queue 3.

At Queue 3 it is executed for 12 seconds and afterward hindered and moved to queue 4.

At Queue 4 it is executed for 17 seconds and afterward hindered and moved to queue 5.

At Queue 5 it executes for 2 seconds and afterward it finishes.

Thus the cycle is intruded on multiple times and finishes on queue 5.

Aging is utilized to guarantee that jobs with lower need will inevitably finish their execution. This method can be utilized to decrease starvation of low priority jobs. There are numerous approaches to execute aging, yet all have a similar rule that the need of a cycle should increment as it holds up in the prepared line.

on the off chance that priority range from 127(low) to 0(high), we could expand the priority of a holding up measure by 1 Every 15 minutes. In the end even a cycle with an underlying priority of 127 would take close to 32 hours for priority 127 cycle to age to a priority-0 cycle.

hardware thread" is a physical CPU or center. Thus, a 4 center CPU can truly uphold 4 hardware threads on the double - the CPU truly is completing 4 things simultaneously. One hardware thread can run numerous product threads. ... As to hardware threads, the OS attempts to plan threads to centers, if there are adequate centers