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Discussion Forum 04...

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Using one of the referenced website articles discuss single-queue versus multiqueue scheduling

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The differences between single-queue scheduling and multi-queue scheduling is discussed below. Single-queue scheduling: All the processes or jobs are scheduled in a single queue is called the single-queue scheduling. The best of thing of this scheduling is the simplicity. There is no need to determine which job is to run first because it works with multiple CPUs. One of the problem for single-queue scheduling is the scalability. For preventing this problem, we inserted some form of locking inside the code. The lock ensures that when the code accesses the queue, it will give good outcomes. This lock can reduce the performance, particularly at the time of increasing the number of CPUs. There is another problem is the cache affinity because each CPU simply picks the next job to run from the globally shared queue, each job ends up bouncing around from CPU to CPU. To handle this problem, we used some of the affinity mechanism to run the processes in the same CPU. There is also facing some load balancing problem. The single-queue scheduling is not scale well due to the synchronization processes. It doesn’t preserve cache affinity.

Multi-queue scheduling: All the processes or jobs are scheduled in multiple queues with multiple CPUs is called the multi-queue scheduling. Here, each queue will follow a particular scheduling discipline like Round Robin scheduling. But, in single scheduling, there is no discipline maintained. When a job enters a queue, it will be on the same queue. It is scheduled essentially independently, thus avoiding the problems of information sharing and synchronization found in the singlequeue approach. MQMS is inherently more scalable than the SQMS. Though

queues are increasing with the increment of the CPUs, lock and cache contention is not a major problem. There is a problem of load imbalance at the time of dealing with multiple CPUs and queues. For, this we use the technique of migration which send the processes to the inactive CPUs.

There is not too much differences between the two scheduling. For having multiple queues, the multi-queue is scheduling is much more advanced than single queue scheduling. Lot of errors can be occur at the time of dealing with this scheduling. It is not the easy task to do so.

References: Arpaci-Dusseau, R., & Arpaci-Dusseau, A. (2015, March). Operating Systems: Three Easy Pieces. Retrieved May 6, 2018, from http://pages.cs.wisc.edu/~remzi/OSTEP/...