A question about the topology of 48 cores system
 

Hi, guys:

I have a 48 cores system, which has 4 packages. Each package contains 12 cores. I have a question about its topology. In each package, why the range of core id is only from 0 to 5, rather than from 0 to 11? It seems like there are two logical processors in the same package sharing a same core id number. But each core only has a single thread.


Thanks,

Hyperthreading? What processor is this?

It is AMD Opteron 6174

I don't think AMD has Hyperthreading.

That CPU has two dies per package and six cores per die, and you say you have four packages.

How many different physical ID's are reported?

The two dies in one package behave (for most SMP considerations) like two different packages, rather than like twice as many cores in one package. So it seems reasonable for you to have eight different physical IDs, and it makes sense that (as you have reported) you have only six different core IDs).

But a lot of licensing is based on CPU packaging, and AMD understands that, so they might report to the OS as one 12-core package rather than indicating the two 6-core internal structure.

Does Linux report 48 total logical processors? If not, are you sure that version of Linux understands that CPU chip? Does the BIOS see/report/enable all 48 cores?

Yes, it reports 48 total logical processors, but only reports physical package ids from 0 to 3. And the cpu is AMD Opteron(tm) Processor 6168.

So there are only four different physical IDs and four different core IDs in /proc/cpuinfo, but 48 different "processor" numbers.

So for each of the twelve combinations of physical ID and core ID there are two different processor numbers.

If I have all that correct, please post two sections of /proc/cpuinfo showing different processor numbers but the same physical ID and core ID. I'm curious especially about what differences there are other than processor number, but also about all the other details of that cpuinfo.

jeffwang66,

When you click "Report" instead of "Quote", your post gets lost; as you may have noticed. :)

Also, it usually isn't necessary to quote the post immediately before your post.

I checked /proc/cpuinfo file, for each core in the same package, one parameter called "apicid" is different. The range of this parameter is from 0 to 11 in each package to label each core I think . Do you know what is it? Does it mean each die in the same package contain six cores ?

Sorry, I need to correct one thing. The value of apicid for each core is different.