Processor Congestion Detection Logic for Multiprocessor Systems
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Solution Overview
Problem
Multiprocessor systems face resource congestion due to repeated access requests and negative acknowledgments when multiple processors attempt to access the same data, leading to system overload and performance degradation.
Innovation Solution
Implementing congestion detection logic within processors to identify resource congestion based on consecutive negative acknowledgments, which triggers a congestion control mechanism to regulate access by increasing the retry time between attempts, thereby preventing system overload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple processors continuously retry access requests after receiving negative acknowledgments, then data access availability is improved, but system congestion increases and performance degrades
Solution Approach 1:
The system implements feedback mechanisms where processors monitor the responses to their access requests. When a processor receives negative acknowledgments, it adjusts its retry behavior based on the observed system state. This feedback loop allows the system to dynamically adapt access patterns, reducing congestion while maintaining data access availability.
Solution Approach 2:
The retry mechanism transitions from a static fixed-attempt approach to a dynamic adaptive approach. Processors dynamically adjust the number of retry attempts and timing based on real-time system conditions indicated by acknowledgment patterns. This dynamic behavior allows the system to balance between maintaining access availability and preventing performance degradation under varying load conditions.
2Reliability
If processors increase retry attempts to ensure data access, then access reliability is improved, but system congestion and overhead increase
Solution Approach 1:
The system changes the parameters of access requests dynamically based on system state. Instead of using a fixed number of retry attempts, processors adjust retry parameters such as the number of attempts and timing intervals based on observed acknowledgment patterns. This parameter adaptation reduces the total quantity of access requests when system conditions permit, while maintaining access reliability when needed.
Solution Approach 2:
The system applies partial retry actions rather than always executing full retry sequences. Processors evaluate whether to perform retries based on system conditions, executing only the necessary portion of potential retry attempts. This selective approach prevents excessive access requests while ensuring adequate retry behavior when data access failures occur.
3Speed
If processors immediately retry access after negative acknowledgment, then access speed is improved, but system congestion increases
Solution Approach 1:
The system implements periodic retry actions with variable intervals rather than immediate continuous retries. Processors introduce timing intervals between retry attempts, adjusting these periods based on system conditions indicated by acknowledgment patterns. This periodic approach maintains access speed by ensuring timely retries while reducing system congestion by spacing out access requests.
Solution Approach 2:
The system prepares for potential congestion by cushioning retry requests with timing intervals before they are sent. Instead of immediately retrying upon negative acknowledgment, processors wait for appropriate intervals that cushion the system against congestion while still maintaining relatively fast access. This prior cushioning prevents harmful congestion effects while preserving acceptable access speed.
Data Source
AI summary
In an embodiment, a system includes a resource. The system also includes a first processor having a load/store functional unit. The load/store functional unit is to attempt to access the resource based on access requests. The first processor includes a congestion detection logic to detect congestion of access of the resource based on a consecutive number of negative acknowledgements received in response to the access requests prior to receipt of a positive acknowledgment in response to one of the access requests within a first time period.