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Jiangv
Beginner
146 Views

what is the connection between skylake-sp die config and cpu core id in system

Hi I am now checking the skylake-sp die topology, and found this pic on internet.

 

die.png

So when I get core id from 0-17 in linux system, how can I know the position of each core.

I mean is there a sequence in physical core tied up with logical core(linux core id)?

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10 Replies
IntelSupport
Community Manager
128 Views

Hello Jiangv


Thank you for posting in the Intel Community. 


We would like to look into your question. To start I would like to know what is the model of the Intel® that you are using to work on this question?

Can you provide us with a picture of the outcome from Linux core id?


Regards,

Leonardo C.


Intel Customer Support Technician


IntelSupport
Community Manager
117 Views

Hello Jiangv,

 

I am checking on your thread to know if you have been able to collect the details requested?

 

Regards,

Leonardo C.


Intel Customer Support Technician


Jiangv
Beginner
96 Views

Thanks Leonardo

lets talk about a 7980xe processor, this is what I get from linux

 

IntelSupport
Community Manager
85 Views

Hello Jiangv


Thank you for your response, I am going to move your request to the correct support forum, you would be contacted soon.


Regards,

Leonardo C.


Intel Customer Support Technician


AndrewG_Intel
Moderator
66 Views

Hello @Jiangv

In order to check this further, could you please provide us with the following details?


1- What are you trying to achieve?

2- Why do you need to know the physical position of each core relative to the information you obtain from Proc_ID?


As far as we know, there is no command in Linux* nor any platform that can map and display each physical core to its assigned logical number as this is done by the microcode for each unit.


Best regards,

Andrew G.

Intel Customer Support Technician


Jiangv
Beginner
60 Views

Thanks Andrew

we want to know the logical core connections with physical core for our app thread allocations, in some circumstances our app's performance is highly related to the core distance.

yes there is no tools that to found out the position of physical cores, that's why we want to ask you guys.

do you think that all logical core is continuous lining up in row or column like the die topology?

could you ask your colleagues who can conform this for us?

really appreciate!

AndrewG_Intel
Moderator
46 Views

Hello Jiangv

Thank you for your response and for the additional details regarding your inquiries.

Please allow us to check this further and we will be posting back in the thread as soon as more details are available.


Best regards,

Andrew G.

Intel Customer Support Technician


AndrewG_Intel
Moderator
35 Views

Hello @Jiangv

Thank you for your patience in this matter.


After checking this further, we would like to inform you that there is no way to determine physical core connection with logical one as this is assigned as per unit and per microcode so it varies.

There are programmatical techniques to optimize thread allocation, per example, please refer to this Developer Guide and Reference

 

For further questions on thread allocation optimization for software development we recommend addressing those concerns to Intel's Developer Zone forums, for instance: Software Development Tools (Compilers, Debuggers, Profilers & Analyzers) forum


Best regards,

Andrew G.

Intel Customer Support Technician


Jiangv
Beginner
31 Views

Thanks Andrew

I also a member of CCE China, so I got this doc, skl-eds-vol1-arch-reg, and find a pic in this doc

微信图片_20210220114834.png

there also a note says " Physical core 0 is in the upper left corner and increments down as shown in the figure above. Note certain modes of the processor will change the physical core numbering"

I think it says maybe some certain model of CPU will change the numbering, but for a certain sku, like i9-7980xe, each one of i9-7980xe should have the same numbering right? 

But from your update, you are sure that every 7980xe cpu has it's own numbering?

If it's true, then could you check how the numbering could change, it changes in randomly? or just change the direction in the above pic.

 

Thanks!

AndrewG_Intel
Moderator
22 Views

Hello Jiangv

Thank you for your response.


We understand that you have additional inquiries, unfortunately, this information is out of our scope but please let me guide you to the place where can address those concerns and find additional assistance from the proper team.

Please kindly post your questions on the Intel Developer Zone forums, for instance: Software Development Tools (Compilers, Debuggers, Profilers & Analyzers) forum


Having said that, we will proceed to close this inquiry now. If you need any additional information, please submit a new question as this thread will no longer be monitored. Thank you for your understanding.


Best regards,

Andrew G.

Intel Customer Support Technician