help interpret lstopo output

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Hello all, I recently followed Gridrunner's excellent tutorial here on how to use the lstopo command to optimize PCI slot assignment, CPU core assignment, etc for best performance of VMs in a multi CPU setup.


I am using a PowerEdge R710, which is a dual CPU board, with 2x Xeon X5690 installed. I was expecting to see output similar to the example in the video, though with 2 CPUs instead of 4, and I'd have to match up which PCI slot is connected to which CPU. Instead this is what I got: 



There are a couple things about this that don't make sense to me:

-why are the numbers of the CPU cores all wonky? They are each 6 cores (12 threads), I'd expect to see them numbered 0-5 and 6-11 or something like that

-why do all the devices seem to be connected to the same CPU? My understanding was each CPU has its own memory and some (but not all) of the PCI lanes, is this not correct?

-what do the numbers (eg 1.0, 2.0, 0.5) on some of the devices mean?

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  • 2 weeks later...

In case anyone is curious how this turned out, I did some research into the Intel 5520 chipset which is on the R710. The architecture seems to use 3 of what Intel calls Quick Path Interconnects to connect the 2 processors together and each processor to the I/O hub. So unlike some other architectures (such as the one in Gridrunner's tutorial) the PCIe slots seem to connect directly to both processors rather than just one or the other.



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