Technology Brief: DMA Coalescing

Network Utilization
Network Power
Energy
Efficient
Ethernet
Platform Power
Interrupt Coalescing
DMA Coalescing
Component Power
Energy Efficient Silicon
Integrated PHY
Increased Port Density
5% 25%
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-efcient
networking for the enterprise. As shown in Figure 2, different
features of Intel Ethernet Power Management Technology
contribute more to power consumption reduction at specic
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 most effective in the 5 to 25 percent range
of network utilization, with maximum benefit at 25 percent.
Industry studies report that most networks experience
utilization rates below 25 percent. Therefore, DMA Coalescing is
broadly advantageous at typical network utilization levels. This
capability, including synchronization of DMA calls across the eight
ports of two Intel® Ethernet I350 quad-port adapters, is unique
to Intel Ethernet Server Adapters; competing products offer no
DMA Coalescing at all.
Network Utilization 25 Percent and Higher:
Low Component Power
While particularly dominant at higher network utilization levels,
low component power is a significant contributor to energy
efficiency in all cases. Integrated quad-port silicon, uniquely
offered by Intel Ethernet Server Adapters, has significant
power and component advantages, compared to a competitor’s
quad-port solution that requires two dual-port adapters, two
controllers, and a bridge chip to coordinate all four ports.
Power Savings for the Energy-Efficient Enterprise
Traditional enterprise applications, ranging from e-mail, to web
servers, to file and print, realize significant cost savings from
DMA Coalescing and the other features of Intel Ethernet Power
Management Technology. Depending on latency requirements,
IT organizations can balance performance with power savings,
another way of controlling operating expense for an ongoing
competitive advantage.
Learn More About Intel® Ethernet: www.intel.com/go/ethernet
Figure 2. Different aspects of Intel® Ethernet Power Management Technology predominate at different levels of network utilization.
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