Access Arbiter Dynamic Priority Control for Mixed Process Arbitration
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Solution Overview
Problem
Existing access arbiters face challenges in efficiently managing real-time and non-real-time processes simultaneously, as they require high processing capabilities and struggle with dynamic priority adjustments, especially in mixed environments where real-time and non-real-time processes share memory resources.
Innovation Solution
An access arbiter with priority holding and control mechanisms that adjust priorities based on elapsed time, allowing for efficient arbitration without complex sorting processes, by increasing priority when lower than a reference level and decreasing it upon access completion, ensuring proper response times and compatibility between real-time and non-real-time processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a round robin method is used to guarantee real-time property, then the worst access time is controlled, but excessively high processing ability is required for processes
Solution Approach 1:
The patent applies dynamic priority adjustment where the priority of each requester changes over time based on elapsed time and access history. Instead of fixed round-robin ordering, the system dynamically modifies priority levels to balance real-time guarantees with processing efficiency, allowing high-priority real-time processes to be served promptly while preventing starvation of lower-priority processes.
Solution Approach 2:
The system changes the priority parameter of requesters based on elapsed time and access patterns. By adjusting the priority value dynamically rather than maintaining fixed priorities, the arbiter can adapt to varying workload conditions and process requirements, resolving the contradiction between real-time guarantees and processing capability.
2Productivity
If EDF method is used for optimum scheduling, then scheduling efficiency is improved, but it is difficult to perform rearranging items in the waiting queue upon each generation of a task using hardware
Solution Approach 1:
The patent pre-calculates and stores priority values for each requester based on elapsed time and access patterns. Instead of performing complex sorting operations when tasks are generated or completed, the system maintains pre-computed priority information that can be quickly compared and used for arbitration, significantly reducing hardware complexity while maintaining EDF-like scheduling efficiency.
Solution Approach 2:
The system uses simplified priority value representations and comparisons rather than full task queue sorting. By copying and comparing priority parameters rather than rearranging entire task structures, the hardware implementation becomes much simpler while still achieving optimal scheduling decisions.
3Reliability
If EDF method is applied to real-time processes, then real-time scheduling is improved, but it is difficult to apply to non-real-time processes which have no distinct deadline
Solution Approach 1:
The patent creates a universal priority adjustment mechanism that works for both real-time processes with deadlines and non-real-time processes without deadlines. The same priority holding and control logic adapts to different process types by interpreting elapsed time and access patterns differently, allowing the system to handle mixed workloads effectively without requiring separate arbitration mechanisms.
Solution Approach 2:
The dynamic priority adjustment mechanism automatically adapts its behavior based on process characteristics. For real-time processes, priority increases with elapsed time to ensure deadline compliance; for non-real-time processes, priority adjusts based on access patterns to achieve fair resource distribution. This dynamic adaptation enables the same hardware to efficiently arbitrate both process types.
Data Source
AI summary
A priority control value, which is smaller as the priority of access by each of requesters is higher, decreases with the lapse of time when an access request is issued. When the access is completed, the priority control value increases by a priority decrease value (PERIOD). When there is no access request, the priority control value decreases to a reference priority value (TMIN) and is then maintained at the reference priority value. Access permission is given to the one of the requesters issuing requests which has the smallest priority control value. As a result, proper arbitration is performed at a high speed with a simple hardware configuration.