Interrupt Moderation, Intel® GbE Controllers: Application Note
This application note describes how to use the interrupt moderation features of the Intel® GbE Controllers. Note: The reader is assumed to have a working knowledge of network device drivers.
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Interrupt moderation reduces host processor interrupts, thereby enabling technologies such as Gigabit EtherChannel* to deliver more of their 16-Gb/s bandwidth potential (8 Gb/s x full duplex). As a result, performance gains from load-balancing used in adapter teaming becomes a smaller part of overall performance as compared to the performance gains achieved through the increased server CPU headroom provided by interrupt moderation.
Host processor interrupts are generated by the GbE controller in order to request cycles for packet processing. These interrupts need to be controlled to achieve optimum throughput. Too few interrupts can lead to latencies and too many can unduly burden the server’s processor. By bundling an appropriate number of packets before issuing an interrupt to the host (Figure 1), the GbE controller tunes interrupt frequency to match traffic conditions while maintaining packet flow.
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