Load Store Unit Dependency Tracking for Deadlock Avoidance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Out-of-order processing in data processing systems can lead to deadlocks when all access slot circuits are busy with bypassing instructions, preventing the issuance of bypassed instructions, resulting in inefficient resource utilization.
Innovation Solution
Implementing dependency tracking circuitry to manage access slot circuits, allowing issuance of bypassing instructions only when a minimum freeable number of circuits is available, ensuring deadlock avoidance while optimizing resource usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If out-of-order processing is implemented to improve instruction throughput, then productivity increases, but deadlock situations may arise when all access slot circuits are busy with bypassing instructions
Solution Approach 1:
The patent applies preliminary action by checking the number of busy access slot circuits before issuing a bypassing instruction. The issue control circuitry prevents issuance of bypassing instructions when the number of busy circuits exceeds a threshold, proactively avoiding deadlock situations before they occur. This anticipatory control mechanism ensures system reliability while maintaining out-of-order processing capability.
2Reliability
If a minimum number of access slot circuits are kept empty to prevent deadlocks, then reliability improves, but resource utilization efficiency deteriorates
Solution Approach 1:
The patent implements dynamics by making the effective number of accessible circuits dynamic rather than static. The issue control circuitry continuously monitors the number of busy access slot circuits and adjusts the availability of circuits dynamically. When the number of busy circuits is below the threshold, bypassing instructions can utilize all available circuits. When the threshold is exceeded, further bypassing is prevented. This dynamic adjustment optimizes resource utilization while maintaining deadlock prevention.
3Reliability
If access slot circuits are held empty to guarantee availability for bypassed instructions, then deadlock avoidance is ensured, but loss of time occurs due to unused resources
Solution Approach 1:
The patent applies feedback by implementing a monitoring mechanism that tracks the number of busy access slot circuits and uses this information to control instruction issuance. The issue control circuitry receives feedback about the current state of access slot circuits and adjusts its control decisions accordingly. This feedback loop eliminates the need to permanently hold circuits empty, as circuits are only restricted when necessary to prevent deadlock, thereby reducing resource idle time while maintaining deadlock avoidance.
Data Source
AI summary
A load store pipeline 18 includes an issue queue 20 and load store circuitry 24. The load store circuitry 24 includes the plurality of access slot circuits 26 to 40. Dependency tracking circuitry 42, 44, 46, 48 serves to track a freeable number of access slot circuits 26 to 42 corresponding to the sum of access slot circuits that are empty and those processing data access instructions which have not bypassed any preceding data access instructions within the program execution order.