CPU Scheduling | Articles | flash animation free download computer graphics Fun pages, download free flash animation.

Home > Articles > Papers > CPU Scheduling

Articles

CPU Scheduling

07 Oct 2006 12:00 AM Author

Sally Ahmed

Processor Scheduling Policies

Scheduling determines which process is chosen to make the transition from the ready state at the processor waiting queue to actually running on the processor. In a multiprocessor system, the scheduling will involve more than one processor, but at any given time, there will be only one process running per processor.

Scheduling algorithms fall into two categories: preemptive and non-preemptive algorithms. Preemptive is when an algorithm, such as Round-Robin, Shortest Remaining Time (SRT), removes a process from the processor when its associated time-slice (quantum) expires, to enable this the next process on the queue is given a higher priority or the waiting-time for other processes is increased. Preemptive reduces overall waiting time and makes such algorithms generally suitable for interactive systems. On the other hand, non-preemptive schedulers, such as First-in-First-Out (FIFO), Shortest Process First (SPF) and Highest-Response-Ratio-Next (HRRN), allow a process to run to its completion or until it voluntarily gives its CPU time. Non-preemptive can result in depriving waiting processes from the processor time in favor of the running process.