Scheduling and factors affecting performance of multicore processor

 Scheduling of multicores

The scheduling of multi core is performed in such a manner that the real time tasks do not miss their deadlines. The scheduling of multicore includes two types of scheduling: Partitioned scheduling and Global scheduling. In partitioned scheduling different tasks are assigned to cores statically and they are not allowed to migrate from one core to another. The partitioned scheduling is advantageous as there is no migration overhead. But, the use of partitioned scheduling suffers two major disadvantages

(a) This scheduling scheme is inflexible in nature and cannot easily accommodate dynamic tasks without a complete re-partition.

(b) It is related to optimal assignment of tasks to cores which creates an NPhard problem for which polynomial-time solutions result in sub-optimal partitions.

Factors affecting performance of multicore processor

The performance of the multicore processor is good if the CPU is utilized properly and the desired outcome is produced in a good response time. Hence following are the main factors that may affect the performance of a multicore processor:

1) Cores configuration: A multicore processor may have two or more cores running on same or different speed. The performance of any multicore processor is affected if the cores are not fully utilized that is the core is idle most of the time. A mechanism should be applied such that the number of idle slots in a core can be reduced resulting in good overall utilization of the system and if the number of idle slots are more then such slots can be combined together to make one big slot in which the core can be made to sleep state.

2) Workload: The workload of multicore processor basically defines the number of tasks: normal or real time tasks, that is to be assigned to the cores of the system. The scalability of workload affects the performance of multicore.

3) Inter Intra core communication: An intercore communication is one in which the two or more cores can communicate via shared memory architecture whereas in intracore communication a core communicates its local cache for any data needed. The more is the intracore communication good will be the performance of the system considering the fact that the hit ratio is good enough than the miss ratio.


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