Overhead Task Partition Margin Diagnostic Tool
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Solution Overview
Problem
In safety-critical systems like avionics, determining the available margin in partitions scheduled by priority preemptive schedulers is challenging due to the complexity of interactions between periodic and aperiodic tasks, making it difficult to assess the system's ability to meet deadlines.
Innovation Solution
A method is introduced that uses a configurable overhead task to consume a specified duration of partition time, allowing the system to reveal partition margins by controlling the execution duration of the overhead task to cause either a periodic task to miss its deadline or reduce available time for aperiodic tasks below a threshold, thereby determining the true margin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional monitoring tools are used to show task execution and maximum utilization, then basic scheduling information is provided, but the actual partition margin cannot be accurately determined due to misleading numbers and complex task interactions
Solution Approach 1:
The patent introduces an intermediary overhead task that mediates between the scheduler and the actual tasks to measure partition margin. This overhead task consumes a controlled amount of partition time and serves as a probe to determine the true available margin, isolating the measurement process from the complex task interactions.
Solution Approach 2:
The patent creates a simplified copy of the partition execution environment by introducing an overhead task that mimics resource consumption without executing actual task logic. This allows measurement of margin in a controlled manner that reflects real conditions without the complexity of actual task interactions.
2Productivity
If aperiodic tasks are allowed to utilize 100% of available time, then maximum resource utilization is achieved, but the available execution budget always appears completely consumed making margin assessment impossible
Solution Approach 1:
The patent applies preliminary action by introducing the overhead task before aperiodic tasks execute. This overhead task pre-consumes a controlled portion of the partition time, ensuring that when aperiodic tasks run at maximum utilization, there is still a measurable remainder that reveals the true partition margin.
3Measurement precision
If execution duration of overhead task is increased to reveal partition margin, then margin measurement becomes possible, but periodic tasks may fail to meet deadlines or aperiodic task time may fall below threshold
Solution Approach 1:
The patent uses parameter changes by systematically varying the execution duration of the overhead task to find the critical threshold. By adjusting this parameter, the system identifies the point where periodic tasks just meet their deadlines or aperiodic tasks just maintain their minimum time requirements, thereby revealing the true partition margin.
Solution Approach 2:
The patent applies partial action by having the overhead task consume only the specific portion of partition time needed to reveal margin, rather than consuming all available time. This partial consumption is calibrated to be excessive enough to reveal the margin boundary but not so excessive as to cause system failure.
Data Source
AI summary
In one embodiment, a method for margin determination for a computing system with a real time operating system and priority preemptive scheduling comprises: scheduling a set of tasks to be executed in one or more partitions, wherein each is assigned a priority, wherein the tasks comprise periodic and/or aperiodic tasks; executing the set of tasks on the computing system within the scheduled periodic time window; introducing an overhead task executed for an execution duration controlled either by the real time operating system or by the overhead task; controlling the overhead task to converge on a point of failure at which a length of the execution duration of the overhead task causes either: 1) a periodic task to fail to execute within a deadline, or 2) time available for the aperiodic tasks to execute to fall below a threshold; and defining a partition margin corresponding to the point of failure.