Bandwidth Allocation Apparatus for Fair Arbitration
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Solution Overview
Problem
Existing arbitration mechanisms in computer systems, such as PCI Express, face challenges in balancing fairness and efficiency in data bus access, leading to potential deadlocks or uneven bandwidth distribution among downstream devices, affecting overall system smoothness.
Innovation Solution
A bandwidth allocation apparatus comprising high and low bandwidth arbitration modules, a multiplexer, and a counting circuit classifies downstream devices into groups based on transmission speed, dynamically switching between modules to allocate access rights and prevent excessive bandwidth usage, ensuring fair and efficient data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an entirely fair arbitration mechanism is used to ensure fairness in bus access, then fairness is improved, but the bus access timing for time-sensitive devices deteriorates, causing deadlocks
Solution Approach 1:
The arbitration mechanism is segmented into multiple independent arbitration units, each handling specific downstream devices. This segmentation allows different fairness policies to be applied to different device groups simultaneously, resolving the contradiction between overall fairness and timely access for specific devices.
Solution Approach 2:
The system dynamically changes arbitration parameters such as priority levels and access weights based on device characteristics and current system state. This allows the arbitration mechanism to adapt between fairness-oriented and efficiency-oriented modes, preventing deadlocks while maintaining overall fairness.
2Duration of action of moving object
If downstream devices are allowed to occupy bandwidth for long periods, then transmission completeness for individual devices is improved, but the smoothness of packet transmission for the entire system deteriorates
Solution Approach 1:
The arbitration mechanism implements periodic access allocation where each downstream device is granted bus access in periodic intervals rather than allowing continuous long-term occupation. This periodic action ensures that no single device monopolizes the bandwidth for extended periods, maintaining smooth packet transmission across the entire system while still providing sufficient access duration for complete transmissions.
Data Source
AI summary
The bandwidth allocation apparatus includes a high bandwidth arbitration module, a low bandwidth arbitration module and a multiplexer. The high bandwidth arbitration module is used to select one downstream device from the high bandwidth downstream device group for allowing uplink. The low bandwidth arbitration module is used to select one downstream device from the low bandwidth downstream device group for allowing uplink. The multiplexer selects the one of the access requests from the high bandwidth arbitration module or the low bandwidth arbitration module for allowing to uplink the access request to an upstream device. The access transmission times of the high bandwidth arbitration module and the low bandwidth arbitration module are counted respectively by a counting circuit.