Interrupt moderation is a technique used in networking to control the rate at which interrupts are generated by network interface cards (NICs) in response to incoming packets. The key goal is to balance the load on the CPU while ensuring that latency in packet processing remains low.
To avoid interference with latency, the interrupt moderation rate should be set based on the typical traffic patterns, application requirements, and overall network performance targets. This typically involves:
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Low Interrupt Moderation Rate: For applications that require low latency, a low interrupt moderation rate would be advisable. This means the NIC will generate interrupts more frequently, allowing packets to be processed quickly and reducing queue buildup. However, this can lead to higher CPU utilization.
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Dynamic/Adaptive Interrupt Moderation: Some modern NICs and operating systems support dynamic or adaptive interrupt moderation, where the system intelligently adjusts the rate of interrupts based on current network conditions and system load. This can help maintain low latency during bursts of traffic while preventing excessive CPU load during quieter periods.
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Fine-Tuning: It is often necessary to fine-tune the interrupt moderation settings to find the right balance for specific workloads. Performance testing can reveal the optimal settings for a given environment.
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Traffic Types: Understand the nature of the traffic. For example, interactive applications (like VoIP, online gaming, etc.) may require more frequent interrupts (thus lower moderation) compared to bulk data transfers (where higher moderation can be beneficial).
In summary, to achieve low latency, you generally want to keep the interrupt moderation rate low enough to avoid delays in packet processing. The exact values can vary based on the hardware, drivers, and application requirements, so testing in your specific environment is always recommended.
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