4 Replies Latest reply on Jan 9, 2018 12:38 PM by Intel Corporation

    Xeon E5 disable DDIO in OS?

    Yifan

      Hi,

       

      Recently we are investigating some functionalities of Xeon CPU (E5 2660 V4), and I know it's possible to enable or disable the DDIO in BIOS(though I could not find this option in the our BIOS GUI). So right now I'm wondering if there could be some ways to enable or disable it in the OS. Maybe this can be implemented by setting/resetting certain register in the CPU?

       

      Another question is, it seems that another technology named DCA (direct cache access) overlaps part of the functions of DDIO, I'm also wondering if there is any difference between this 2 technologies, or it's just the same thing with different terms....... it seems like DCA is a sub-set of the ioat, and ioat is at the same hierarchy  as DDIO.

       

      here are some references

       

      1. DDIO

      Intel® Data Direct I/O Technology

       

      2. disable DDIO in BIOS

      https://communities.intel.com/thread/109605?q=Xeon%20E5%20disable%20DDIO

       

      3. ioat/DCA

      Intel® I/O Acceleration Technology

       

      4. possible differences between DCA and DDIO (it's provided by vmware and is not an official one), it also mentions how to disable DDIO through register, but I'm not sure if it's the correct way.

      Revisit DCA, PCIe TPH and DDIO

        • 1. Re: Xeon E5 disable DDIO in OS?
          Intel Corporation
          This message was posted on behalf of Intel Corporation

          Hi : 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.
           
          Regards,
          Alberto R
           

          • 2. Re: Xeon E5 disable DDIO in OS?
            Intel Corporation
            This message was posted on behalf of Intel Corporation

            : 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.
             
            Regards,
            Alberto R
             

            • 3. Re: Xeon E5 disable DDIO in OS?
              Yifan

              Thanks a lot! Your answers are quite helpful.

              • 4. Re: Xeon E5 disable DDIO in OS?
                Intel Corporation
                This message was posted on behalf of Intel Corporation

                : Perfect, you are very welcome.
                 
                Any other inquiry, do not hesitate in contact us again.
                 
                Regards,
                Alberto R