Question about cache consistency when using DDIO(DCA)

[Hoddy]

Hi,

I perform some tests on DDIO and find the Page 8 in PPT (https://www.dpdk.org/event/dpdk-summit-china-2018/roman-sudarikov-dpdk_prc_summit_sudarikov/) about controlling DDIO.

I did observe performance changes by modifying the configurations of registers in the same way as Option 1, 2 and 3 in the PPT, so I feel these are correct.

It shows that when set the "Disable_all_allocating_flows" to "0" and "NoSnoopOpWrEn" to 1,  it is possible to control the DDIO per PCI Transaction by changing "TLP NS Bit" (e.g. setting this Bit to "0" to enable DDIO). However, this approach turns off "Snoop" ("NoSnoopOpWrEn" to 1)

I wonder that, is this "Snoop" a snooping protocol to guarantee consistency between cache and DRAM? If so, accoding to Option 4 and 5 in the PPT, if I first write object using version One to LLC with "TLP NS bit" set to 0 (i.e., DDIO on), and then write the same object using version Two to DRAM with "TLP NS bit" set to 1 (i.e., DDIO off), will this cause the object in the DRAM to be newer than that in the LLC?

Best Regrads

[JayB_Intel · Accepted solution]

Hello Hoddy,

Thank you for contacting us regarding the DDIO(DCA). Please be advised that for software related topics we have a dedicated team that are handling Intel Developer Zone related queries. I would strongly suggest to consider posting a question on the appropriate subforum topic below for further assistance:

https://community.intel.com/t5/Developer-Software-Forums/ct-p/developer-software-forums

Alternatively, you may consider submitting a case via service request below and our dedicated team that can provide appropriate support will revert to you the soonest:

https://www.intel.com/content/www/us/en/support/contact-intel.html#support-intel-programs_91207

I hope this helps. If you need any additional information, please submit a new question as this thread will no longer be monitored. Thank you, keep safe and all the best!

Best regards,

Jay B.

Intel® Customer Support Technician

[Hoddy]

Hi,

Thanks for your reply. Sorry for choosing an unrelated category. I have post the question on the software topic.

Best regards