Adaptive Interrupt Moderation for Network Interface Controllers
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Solution Overview
Problem
Computer systems handling high packet communication traffic face significant CPU burdens due to frequent interrupts from network interface controllers (NICs), which existing adaptive interrupt moderation techniques do not adequately address, as they require optimal settings that vary with traffic patterns and channel characteristics.
Innovation Solution
The method involves measuring average throughput rates across multiple active rings and dynamically setting interrupt moderation parameters for each ring based on comparisons to the average rate, classifying rings into idle, latency, mid-range, and high-throughput modes, and adjusting timeout periods and packet counts accordingly to optimize interrupt rates and reduce CPU load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If interrupt moderation is applied to reduce interrupt rates, then CPU load is reduced, but packet delivery latency increases
Solution Approach 1:
The patent implements dynamic interrupt moderation where the NIC adapts interrupt rates based on real-time traffic conditions. The system monitors packet arrival rates and dynamically adjusts moderation parameters, allowing aggressive moderation during low-traffic periods (reducing CPU load) while maintaining responsive interrupt rates during high-traffic periods (minimizing latency).
Solution Approach 2:
The system changes interrupt moderation parameters based on traffic patterns. Different moderation thresholds and timing parameters are applied depending on whether traffic is characterized by bursty patterns or steady flows, optimizing the balance between CPU load reduction and latency performance for each traffic type.
2Productivity
If adaptive interrupt moderation adjusts interrupt rates based on traffic patterns, then CPU load is optimized, but device complexity increases
Solution Approach 1:
The NIC implements self-service adaptive interrupt moderation by autonomously monitoring its own traffic patterns and adjusting interrupt rates without external intervention. The hardware includes built-in logic to detect traffic characteristics and modify moderation behavior, eliminating the need for complex external control systems.
Solution Approach 2:
The system employs feedback mechanisms where the NIC monitors packet arrival patterns and uses this information to adjust interrupt moderation parameters. The feedback loop continuously adapts interrupt rates based on observed traffic characteristics, enabling intelligent optimization without requiring complex external control infrastructure.
3Quantity of substance
If packet aggregation threshold is increased to maximize aggregation count, then interrupt rate is reduced, but packet delivery latency increases in low packet rate scenarios
Solution Approach 1:
The patent implements dynamic packet aggregation thresholds that adapt to traffic conditions. During high-traffic periods, higher aggregation thresholds are applied to maximize batching and reduce interrupt frequency. During low-traffic periods, thresholds are lowered to ensure timely packet delivery, preventing excessive latency for individual packets.
Solution Approach 2:
The system changes aggregation parameters based on traffic rate characteristics. For bursty high-rate traffic, aggressive aggregation is applied. For steady low-rate traffic, less aggressive aggregation or immediate interrupt generation is used, optimizing the balance between aggregation efficiency and latency for each traffic pattern.
Data Source
AI summary
A method for communications includes receiving in a network interface controller (NIC) of a host computer incoming data packets from a network on multiple active rings. An average throughput rate of the incoming data packets is measured over the active rings. For each ring among a plurality of the active rings, a respective throughput rate of the incoming data packets on the ring is measured, and a respective interrupt moderation parameter of the ring is set responsively to a comparison of the respective throughput rate on the ring to the average throughput rate. Interrupts are issued from the NIC to a central processing unit (CPU) of the host computer in response to the incoming data packets on the ring at a rate determined in accordance with the respective interrupt moderation parameter.