LLC prefetch

[countingStars]

I recently learned about the LLC prefetcher for the intel Xeon processor family and read in the "4th Gen Intel® Xeon® Scalable Processor XCC (Codename Sapphire Rapids) Uncore Performance" manual about the "LLCPrefData" and the "DRd_Pref" and other prefetch events, I would like to know if the essential difference between these 2 events is that they prefetch to different destinations, i.e. to LLC and L2 cache respectively? Will these 2 events overlap (i.e. is it possible that an LLCPrefData request will be converted into a DRd_Pref request or something like that)? I've been monitoring the throughput of these 2 events lately and noticed that the throughput for the DRd_Pref event looks odd when LLC Prefetch is open.

[Amina_Sadiya]

Hello countingStars,

Greetings from Intel!  

Thank you for contacting Intel. To proceed further with your query, I kindly request that you share the below details: 

1. Product details 
2. System details  
3. Elaborate the issue that you are facing. 

Please feel free to respond to this email at your earliest convenience. 

Regards, 

Amina 

Intel Customer Support Technician 

[countingStars]

Dear Mr. Amina,

Thank you very much for your reply. But the description of the problem is too complex, perhaps if you could please tell me what is the difference between the LlcPrefData event and the DRd_Pref event in the uncore performance monitor, (document number 639667, CPU model Intel(R) Xeon(R) Silver 4410Y)? Do they convert to each other under certain conditions?

Thank you for your attention to this email.

Regards,

countingStars

[Amina_Sadiya]

Hello countingStars,

Greetings from Intel!  

Thank you for your response, kindly allow me sometime to check this internally and get back to you with an update.

Best regards,

Amina

Intel Customer Support Technician

[vish1]

Hello countingStars,

Greetings!!

The difference between the LLC_PREF_DATA event and the DRD_PREF event in the uncore performance monitor on 4th generation Intel Xeon processors is primarily based on the type and location of the data prefetching they monitor:

• LLC_PREF_DATA Event:
  • This event monitors data prefetches that are targeted specifically at the LLC.
  • It tracks the occurrences where data prefetch requests are made to the LLC.
  • This event is useful for understanding how often data prefetches are occurring at the last level of cache, which can help in analyzing cache behavior and efficiency.

• DRD_PREF Event:
  • This event monitors data read prefetches.
  • Unlike LLC_PREF_DATA which is specific to LLC, DRD_PREF event monitors data prefetches in general, likely at different levels of the memory hierarchy.
  • It helps in understanding the behavior of data read prefetches, which can be important for optimizing memory access patterns and improving overall system performance.

If there are any additional questions, it is recommended to contact PerfMon support (https://perfmon-events.intel.com/)

PerfMon Support

For any questions, please

• Open a GitHub Issue on https://github.com/intel/perfmon
• Email perfmon-support@intel.com

Best Regards,

Vishal Shet P

Intel Customer Support Technician

[Amina_Sadiya]

Hello countingStars,

Greetings from Intel!

Could you please confirm  if you had a chance to look into the information we have shared previously and provide us an update on the same. 

Also please let us know if there is anything else we can assist you with.

Best regards,

Amina

Intel Customer Support Technician

[countingStars]

Dear Mr. Amina,

I sincerely apologize for seeing the message today. Your reply has partially addressed my questions and provided valuable insights. I truly appreciate the time and effort you dedicated to clarifying these points.

Regards,

countingStars

[Amina_Sadiya]

Hello countingStars,

Greetings of the day! 

Thank you for confirmation. Please let us know if you have any further questions or concerns. If No, Could you please confirm if we can go ahead and close this case. 

kindly reach out to us we are happy to help you. 

Regards,  

Amina  

Intel Customer Support Technician  

[Amina_Sadiya]

Hello countingStars,

Greetings of the day! 

This is a follow up on this case, Please let us know if you have any further questions or concerns. If No, Could you please confirm if we can go ahead and close this case. 

kindly reach out to us we are happy to help you. 

Regards,  

Amina  

Intel Customer Support Technician 

[Amina_Sadiya]

Hello countingStars,

Greetings of the day! 

This is a follow up on this case, Please let us know if you have any further questions or concerns. If No, Could you please confirm if we can go ahead and close this case. 

If we don't hear back from you, we'll assume the issue has been resolved and will proceed to close the case. 

kindly reach out to us we are happy to help you. 

Regards,  

Amina  

Intel Customer Support Technician 

[countingStars]

Hi Amina，

Thank you for your follow-up. I confirm that the issue has been resolved, and you may proceed to close this case.
No further questions at this time.

Best regards,

countingStars

[Amina_Sadiya]

Hello countingStars,

Thank you for confirmation. We will go ahead and close this case. 

Thank you for your time and cooperation. It would be great if you could spare some of your time and provide us a feedback on the service provided. Your input will help us improve our support. 

“You may receive an invitation to take a survey in a few days. We value your feedback and look forward to hearing about your support experience.” 

kindly reach out to us we are happy to help you. 

Regards,  

Amina  

Intel Customer Support Technician