FIT2100 Lecture Notes - Lecture 6: Batch Processing, Transaction Processing System, Computer Multitasking
31 May 2018
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Lecture 6/Tute 4 - UNIPROCESSOR SCHEDULING
Processor Scheduling
-To assign processes to be executed by the processor in a way that meets system objectives,
such as response time, throughput and processor efficiency
Types of Scheduling:
Long-Term Scheduling — The decision to add to the pool of processes to be executed
-Determines which programs are admitted to the system for processing
-Controls the degree of multiprogramming
-The more processes that are created, the smaller the percentage of time that each process
can be executed
-May limit to provide satisfactory service to the current set of processes
Medium-Term Scheduling — The decision to add to the number of processes that are partially or
fully in main memory
-Part of the swapping function
-Swapping-in decisions are based on the need to manage the degree of multiprogramming
-Considers the memory requirements of the swapped-out process
Short-Term Scheduling — The decision as to which available process will be executed by the
processor
-Known as the dispatcher or CPU scheduler
-Executes most frequently
-Makes the fine-grained decision of which process to execute next
-Invoked whenever an event occurs (e.g. clock interrupts, I/O interrupts, system calls, signals)
-May lead to blocking of the current process or
-May provide an opportunity to preempt a currently running process in favour of another
-Main objective is to allocate processor time to optimise certain aspects of system behaviour
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Document Summary
To assign processes to be executed by the processor in a way that meets system objectives, such as response time, throughput and processor efficiency. Long-term scheduling the decision to add to the pool of processes to be executed. Determines which programs are admitted to the system for processing. The more processes that are created, the smaller the percentage of time that each process can be executed. May limit to provide satisfactory service to the current set of processes. Medium-term scheduling the decision to add to the number of processes that are partially or fully in main memory. Swapping-in decisions are based on the need to manage the degree of multiprogramming. Considers the memory requirements of the swapped-out process. Short-term scheduling the decision as to which available process will be executed by the processor. Known as the dispatcher or cpu scheduler. Makes the fine-grained decision of which process to execute next.
