[cfarm-users] Fixing CPU/core/threads count

[Segher Boessenkool]

Hi!

On Sat, Apr 04, 2020 at 08:28:49PM +0200, Baptiste Jonglez via cfarm-users wrote:
> Following up on a thread from 2018 [1], we still have issue with counting
> the number of CPU, cores and threads on "exotic" machines.
> 
> I gave a try at hwloc on all farm machines, below is the result where:
> 
> M = machine
> N = node (NUMA node)
> P = package
> C = core
> T = pu (thread)

Other than "M", and perhaps "T", what do those things even *mean*?

Mapping this to the various ways this is expressed on different
architectures (all of those an approximation as well), is more of a
judgment call than a science, as well.

And, the way it is exposed (from system firmware to the OS, say) often
is really only used for one thing: scheduling decisions.  So you also
get the nasty situation that the description might not match reality as
well as it could, but older software will use the hardware better with
it than with a "better" description!


Segher