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Dynamic Program Priority in Multi-Tasking Systems

IP.com Disclosure Number: IPCOM000061549D
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 3 page(s) / 39K

Publishing Venue

IBM

Related People

McDermott, MJ: AUTHOR [+3]

Abstract

Dynamic Program Priority (DPP) varies a task's priority based on task behavior and system events to provide the following functions: ΠA user can assign fixed or variable priorities. Each specifiable priority has a base value. Variable priority may vary above or below its base value. Fixed priority is only allowed to vary above its base value. This allows the user to indicate which jobs will receive preference in service. ΠInteractive operations (workstation input), keep the task priority at or above its base priority value. This provides preference for interactive tasks relative to batch tasks. ΠEach workstation supported by a task increases the task priority above its base priority value. This provides equal service per workstation. ΠPriority is decreased for resource usage.

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Dynamic Program Priority in Multi-Tasking Systems

Dynamic Program Priority (DPP) varies a task's priority based on task behavior and system events to provide the following functions: OE A user can assign fixed or variable priorities. Each specifiable priority has a base value. Variable priority may vary above or below its base value. Fixed priority is only allowed to vary above its base value. This allows the user to indicate which jobs will receive preference in service. OE Interactive operations (workstation input), keep the task priority at or above its base priority value. This provides preference for interactive tasks relative to batch tasks. OE Each workstation supported by a task increases the task priority above its base priority value. This provides equal service per workstation. OE Priority is decreased for resource usage. This prevents a task that monopolizes a resource from degrading the performance of other jobs. This also provides preference for interactive tasks relative to batch. OE On resource conflicts, the priority of the resource owner is temporarily upgraded to the priority of the highest waiter. This prevents a resource from becoming a bottleneck. OE All priority functions are integrated. For example, a user- assigned priority does not negate priority change for resource conflicts or resource usage. The system processes requests for service by scanning queues that are maintained in task priority order. For example, dispatching and preempting for the processor is by task priority, determining the contents of storage is by task priority, disk I/O is done in task priority order, and SVCs (Supervisor Call Instructions) are processed in task priority order. A task's priority is fixed at user-assigned values, fixed at system values pre-assigned by the system for system tasks, or variable (assigned by the user or defaulted by the system). DPP varies a task priority based on its behavior. The upper limit is just below system level priority. For variable priority, the lower limit is the system minimum value. For each allowable fixed priority, the lower limit is a base value. A task's base priority is incremented by a fixed amount for each workstation the task suppor...