Intel® Data Direct I/O Technology (Intel® DDIO) is a feature introduced with the Intel® Xeon® processor E5 family and Intel® Xeon® processor E7 v2 family as a key feature of Intel® Integrated I/O. Intel DDIO is the latest Intel innovation in intelligent, system-level I/O performance improvements. Intel created Intel DDIO to allow Intel® Ethernet Controllers and adapters to talk directly with the processor cache of the Intel Xeon processor E5 family and Intel Xeon processor E7 v2 family. Intel DDIO makes the processor cache the primary destination and source of I/O data rather than main memory, helping to deliver increased bandwidth, lower latency, and reduced power consumption.
Intel DDIO re-architects the flow of I/O data into and out of the processor
The “classic” I/O mode—prior to Intel DDIO—dates from an era when I/O was slow and processor caches were a small, scarce resource. Classically, incoming data from an Ethernet controller or adapter went first into the host processor's main memory. When the processor wanted to operate on the data, it then read the data into cache from memory. Thus, a memory write and a memory read occurred before the processor even did anything with the data. Conversely, outgoing data from the processor to the external I/O first triggered a read from memory to cache followed by a write back to memory as the data evicted from cache. In architectures prior to the Intel Xeon processor E5 family and Intel Xeon processor E7 v2 family, an additional, speculative read would be triggered from the I/O hub.
The world has changed. 10 Gigabit Ethernet (10 GbE) is being adopted broadly in the data center, and with the Intel Xeon processor E5 family and Intel Xeon processor E7 v2 family, last-level cache is now 20 MB, no longer a scarce resource. The insight behind Intel DDIO is to recognize that the classical model’s multiple memory accesses, which degrade performance and increase system power consumption, can be eliminated with a more efficient flow of I/O data by making the processor cache the primary destination and source of I/O data.
Increased bandwidth, reduced latency, and reduced power consumption
The mix of these benefits in a particular server or workstation depends on the workload:
- I/O-bound workloads characteristic of telecom, data plane, and appliances can see dramatic, scalable performance benefits and reduced power consumption.
- Data center workloads that are not I/O bound or response-time critical will benefit primarily from reduced power consumption.
- Applications where response time is critical, such as financial trading and high-performance computing, will see lower latency as well as substantially higher transaction rates.
Intel DDIO is enabled by default on all Intel Xeon processor E5 family and Intel Xeon processor E7 v2 family platforms. Intel DDIO has no hardware dependencies and is invisible to software, requiring no changes to drivers, operating systems, hypervisors, or applications. All I/O devices benefit from Intel DDIO, including Ethernet, InfiniBand*, Fibre Channel, and RAID.