The docs for Hwloc library state that the logical indices of Processor units used by Hwloc are not the same as the indices used by OS.
- How does one map Hwloc logical indices to OS indices?
- Is this functionality exposed in Hwloc.jl wrapper?
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AFAIU, that can be system / OS dependent. So there is no unique answer here.
No, because of the above.
In ThreadPinning.jl (which only works on Linux) I parse the output of lscpu --all --extended to get the OS indices.
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Actually, it seems that Hwloc objects store both logical index assigned by Hwloc and an index assigned by os. Look at the picture at the bottom of this page.
Ok. Now I am really confused.
I looked at this line in the source code of Hwloc.jl.
What I see, is that all hwloc objects indeed have the field os_index. It is actually used to print the topology.
It seems, that I can get the os indices of all processing units by doing
using Hwloc
collectobjects(:PU) .|> x->getproperty(x, :os_index)
@carstenbauer Do you want to say, that the field os_index does not actually correspond to the index used by OS?
I believe to remember that I had a case where hwloc and lscpu didn’t agree but maybe I’m hallucinating. Sorry that I can’t clarify. Given that the field is called os_index I would think (and hope) that it’s correct and what you’re looking for.
Could it be that you compared an hwloc logical_index with the output of lscpu?
If you really observed a discrepancy, may be it is a good idea to file an issue with the hwloc library. Yeah, if only we had time for everything.