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TECHNOLOGY BRIEF Intel® Ethernet Server Adapters DMA Coalescing

Reducing Data Center Power Consumption with DMA Coalescing Intel® Ethernet Server Adapters are the only networking hardware in the industry to offer Direct Memory Access (DMA) Coalescing, which can reduce platform power by as much as 8 to 12 watts. Data center operators must strive to reduce utility costs as a component of operating expense to remain competitive. This requirement has led to the demand for higher energy efficiency in computer platforms, but data centers also need peak performance to meet growing business needs. The optimal balance between energy efficiency and performance is typically obtained by operating at maximum performance for short durations when needed and then returning to low power states. Direct memory access (DMA) is one approach to taking advantage of that principle by adding intelligence to the way processor, chipset, and memory power states respond to DMA interrupts. System components shift into low power states to reduce energy consumption when network traffic levels and other workload characteristics allow. The arrival of network data causes the DMA controller to issue an interrupt command that wakes the processor, chipset, and memory into higher power states. Intel® Ethernet Server Adapters uniquely offer DMA Coalescing, an innovative capability that batches together DMA interrupts to be sent to the system for efficient processing. This capability optimizes the utilization of system resources and allows them to return to a lower power state more quickly than would otherwise be possible. Key aspects of DMA Coalescing are shown in Figure 1. DMA coalescing in Intel® Ethernet Power Management Technology: Interrupts can be synchronized across the eight ports of two quad-port Intel® Ethernet Server Adapters Power Consumption DMA Coalescing batches DMA interrupts so the system can stay in lower power states longer Competitive multi-chip architectures provide no coalescing Power Consumption Asynchronous network traffic limits system time in low power states Figure 1. Intel® Ethernet Server Adapters are the only network hardware in the industry to offer DMA Coalescing, which lowers overall power consumption. Complementary Aspects of Intel® Ethernet Power Management Technology DMA Coalescing is one aspect of a larger set of capabilities known collectively as Intel Ethernet Power Management Technology. These capabilities work together to create more energy-efficient networking for the enterprise. As shown in Figure 2, different features of Intel Ethernet Power Management Technology contribute more to power consumption reduction at specific network-utilization levels. Network Utilization 5 Percent and Lower: Energy Efficient Ethernet Intel Ethernet support for Energy Efficient Ethernet (IEEE 802.3az) is most effective at low network traffic levels, taking advantage of low utilization to keep the link in a low power state as much as possible. This silicon-resident feature enables the Intel Ethernet Server Adapter to negotiate with the network switch ports connected to it. Adapter and switch ports enter and exit low power states together, saving dramatically on energy efficiency. DMA Coalescing shows no significant benefit at such low utilizations because not much data is transferred at such low data rates. Network Utilization 5 to 25 Percent: DMA Coalescing DMA Coalescing is Read the full TECHNOLOGY BRIEF Intel® Ethernet Server Adapters DMA Coalescing.

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