Dynamic Interrupt Moderation for Network Interface Controllers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing adaptive interrupt moderation techniques in computer systems are limited by their reliance on predefined profiles, which restrict flexibility in accommodating dynamic changes in incoming traffic and resource availability, especially when multiple queues are involved.
Innovation Solution
The system dynamically adjusts interrupt moderation parameters for each queue by continuously monitoring throughput and interrupt rates, updating parameters based on comparisons between current and previous periods to maximize packet throughput while minimizing interrupt rates, without relying on predefined profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If interrupt moderation is used 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 continuously monitors traffic patterns and packet rates, adjusting interrupt thresholds and timing in real-time based on current network conditions. This allows the system to optimize between CPU load reduction and latency minimization by adapting parameters such as interrupt coalescing intervals and packet aggregation thresholds dynamically rather than using fixed moderation settings
Solution Approach 2:
The system changes key parameters including interrupt thresholds, coalescing intervals, and aggregation packet counts based on monitored traffic characteristics. When traffic patterns indicate high latency sensitivity, the NIC reduces aggregation thresholds and shortens coalescing intervals, thereby reducing latency while maintaining moderate interrupt rates. Conversely, during low-traffic periods, parameters are adjusted to maximize CPU efficiency
2Adaptability or versatility
If adaptive interrupt moderation is implemented to handle dynamic traffic patterns, then system responsiveness improves, but device complexity increases
Solution Approach 1:
The NIC incorporates self-service capabilities through embedded intelligence that autonomously monitors its own performance metrics, detects traffic pattern changes, and adjusts interrupt moderation parameters without external intervention. The controller includes dedicated logic for tracking packet rates, calculating optimal thresholds, and modifying operational parameters, thereby reducing the burden on host CPU while maintaining adaptability
Solution Approach 2:
The system implements feedback loops where the NIC continuously monitors packet arrival rates, interrupt handling performance, and queue depths, then uses this feedback to dynamically adjust moderation parameters. The controller compares current performance against target metrics and automatically tweaks thresholds and timing to optimize both responsiveness and resource utilization, creating a closed-loop control system
3Productivity
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 adjustment of packet aggregation thresholds based on real-time traffic rate monitoring. During high packet rate periods, the NIC increases aggregation thresholds to maximize packet consolidation and reduce interrupt frequency. During low packet rate periods, the threshold is automatically reduced to minimize waiting time, ensuring packets are delivered promptly even if aggregation count is lower
Solution Approach 2:
The system dynamically changes the packet aggregation threshold parameter based on observed traffic characteristics. When the monitored packet arrival rate falls below a certain threshold, the NIC reduces the aggregation count requirement, allowing interrupts to be generated after fewer packets. This parameter adaptation prevents excessive latency in low-traffic scenarios while maintaining high aggregation benefits during peak traffic
Data Source
AI summary
Apparatus for communications includes a CPU, a system memory, and a network interface controller (NIC), which is configured to receive incoming data packets from a network, to post the received data packets in a designated queue for delivery to the CPU. The NIC issues interrupts to the CPU in response to the incoming data packets at a rate determined, for the designated queue, in accordance with an interrupt moderation parameter that is set for the queue. During each of a succession of monitoring periods, the CPU measures for the designated queue a current throughput of the incoming data packets and a current rate of interrupts, makes a comparison between the current measured throughput and rate of interrupts to the throughput and rate of interrupts that were measured during a preceding period in the succession, and selects and applies an update to the interrupt moderation parameter responsively to the comparison.