Hi Yifan: Thank you very much for contacting the Intel® Processors communities. We will do our best to provide the information you are looking for.
In regard to your inquiry, we will do further research on this matter, as soon as I get any updates I will post all the details on this thread.
Any further questions, please let me know.
Yifan: I just received an update in this matter:
1- Intel® Data Direct I/O (DDIO) is enabled by default in all Intel® Xeon processor E5-based servers. The only way available to disable/enable this feature is in BIOS if the motherboard has that option. In this case you can always check with OEM board manufacturer to see if current Firmware is up to date, or need an update.
2- With Intel® DDIO, Intel's Ethernet server NICs and controllers talk directly to the processor cache without a detour via system memory. Intel® DDIO makes the processor cache the primary destination and source of I/O data rather than main memory. By avoiding system memory, Intel® DDIO reduces latency, increases system I/O bandwidth, and reduces power consumption due to memory reads and writes.
3- Regarding Direct Cache Access (DCA) it allows a capable I/O device, such as a network controller, to place data directly into CPU cache, reducing cache misses and improving application response times.
4- DDIO only works with the local CPU regarding the NIC, DCA may work with any CPU.
Any questions, please let me know.