Interrupt Moderation Circuitry for Host Processor Load Reduction
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Solution Overview
Problem
In networked applications, managing interrupts to preserve quality of service (QoS) is challenging, especially when dealing with numerous queues required for high-performance computing and cloud storage, as existing methods often lead to overloading of host processors due to barrages of network-triggered interrupts.
Innovation Solution
A system with a memory circuit, direct memory access (DMA) circuit, and interrupt engine that stores completion queues and issues interrupt messages only when specific trigger conditions are met, allowing for multiple interrupt moderation modes to control when interrupts are sent to the host processor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If interrupt moderation is applied to reduce interrupt burden on host processor, then host processor performance is improved, but interrupt response time may increase
Solution Approach 1:
The interrupt moderation system dynamically adjusts the moderation parameters (such as threshold values and time constants) based on system conditions and interrupt patterns. This allows the system to optimize between processing load reduction and response time, adapting to different operational scenarios rather than using fixed moderation parameters.
Solution Approach 2:
The system implements feedback mechanisms that monitor interrupt patterns, host processor load, and response time metrics. Based on this feedback, the interrupt moderation circuit adjusts its behavior to maintain optimal performance, ensuring that response time requirements are met while still providing load reduction benefits.
2Adaptability or versatility
If multiple interrupt vectors are provided to handle many queues, then queue processing capability is improved, but host processor complexity increases
Solution Approach 1:
The interrupt handling functionality is segmented between the interrupt moderation circuit (which handles queue monitoring and interrupt generation) and the host processor (which handles high-level processing). This segmentation allows multiple queues to be managed without proportionally increasing host processor complexity, as the moderation circuit handles the granular queue-level operations.
Solution Approach 2:
The interrupt moderation circuit acts as an intermediary between the multiple queues and the host processor. It aggregates interrupt information from multiple queues and presents processed interrupt requests to the host processor, reducing the direct complexity burden on the processor while maintaining the ability to handle many queues.
3Reliability
If interrupts are issued for every completion descriptor, then processing completeness is improved, but host processor load increases
Solution Approach 1:
Instead of issuing interrupts for every single completion descriptor, the system applies partial action by issuing interrupts only when certain conditions are met (such as threshold-based aggregation or time-based batching). This reduces the number of interrupt requests to the host processor while still ensuring that processing is initiated when appropriate, balancing completeness with load reduction.
Data Source
AI summary
A memory circuit is configured for storage of completion queues. Each completion queue can store completion descriptors associated with transfers of data from interrupt source circuits to the memory circuit. A direct memory access circuit provides access to the memory circuit for the interrupt source circuits. An interrupt engine issues interrupt messages for processing the completion descriptors in the completion queues in response to satisfaction of a set of trigger conditions specified in an active interrupt moderation mode. The active interrupt moderation mode is one of multiple available interrupt moderation modes. The interrupt engine bypasses issuing interrupt messages in response to the set of trigger conditions of the active interrupt moderation mode not being satisfied.