AMD CPU find out which cores belong to which CCD

MattSimpson

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Hi All,
There is a performance penalty if an application runs on cores that are on e.g. two distant CCDs I reckon they also call them chiplets.
I am looking at AMD Milan 7543 32-core model. I reckon it comprises of 4x 8-core CCDs.
In the BIOS you can make all on a single NUMA0 or 2 or 4 NUMA system but in this exercise we pursue a single NUMA configuration.
I reckon
0-7 - CCD 1
8-15 - CCD 2
16-23 - CCD 3
24-32 - CCD 4

So the application should run in one of those ranges but it would be good to know which next CCD to use if I need more cores.

Do you know how to workout the layout of the AMD processor on Linux?
Best
 


Brickwizard

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I think you will find it has 8 dies of 4 cores, each core having 2 threads
 
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MattSimpson

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Yes, you are right there is 8 CCDs CDD0 up to CCD7.
These CDDs are configured in couples (I think AMD calls them quadrants) where they share the I/O hub and UMC memory links so technically it should be the most efficient for the respective workloads to run in the same quadrant.
 

Brickwizard

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That I am sorry to say is as much as I can tell you, I could not find anything more than this in the manuals as it's not the sort of information normally given to any of the hardware engineers I know. As it is not a repairable item.
 
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MattSimpson

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No worries, I think I figured it out. The idea is to have the relevant hardware e.g. storage or NIC and the respective application that writes to or reads from in the same quadrant if not possible (no cores left) then in the neighbour quadrants but definitely not in the DIAGONAL quadrant. So for Quadrant 1 - Quadrants 2 & 3 are fine but not Quadrant 4. For Quadrant 2 - Quadrants 1 & 4 is fine but not Quadrant 3 and so on.

Now I just have to test it :)
 
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