[cfarm-users] Correct number of CPU/cores/threads (Was: Setting up GitLab CI for git.git on the farm)

Baptiste Jonglez baptiste at bitsofnetworks.org
Thu Dec 20 12:49:59 CET 2018


On 26-11-18, Segher Boessenkool via cfarm-users wrote:
> On Tue, Nov 27, 2018 at 12:10:27AM +0100, Brice Goglin via cfarm-users wrote:
> > Instead of hardwiring Linux-specific things, many projects now just use
> > hwloc [1] to get such kind of topology information in a portable way
> > (that's what I use cfarm for). On the command-line, you'd just do
> > "hwloc-calc -N core all" to get the number of cores, but there's also a
> > C API to do that.
> Cool stuff :-)
> gcc110 (a power7, 2 packages, 16 cores, 64 threads):
> gcc112 (a power8, 2 DCMs (i.e. 2 packages, 4 dies), 20 cores, 160 threads):
> gcc135 (a power9, 2 packages, 32 cores, 128 threads):

So, I just added pretty usage bars [1] to the list of machine :)

Since I needed the correct number of cores/threads to compute a percentage
of CPU usage, I took the opportunity to manually fix the cases where
Ansible gets it wrong:

- EdgeRouters: gcc22, gcc23, gcc24
- Mustang aarch64 boards: gcc113, gcc114, gcc115, gcc116
- Opteron aarch64 boards: gcc117, gcc118
- POWER machines running Linux: gcc110, gcc112, gcc135

If you see any other wrong CPU information in https://cfarm.tetaneutral.net/machines/list/
I can also fix it.  For instance, the number of cores/threads for the AIX
machines looks incorrect, but I have no idea how to get the correct
information (does hwloc even build on AIX?).

I realize now that "CPU" vs "cores" is a simplistic distinction for some
machines.  I tend to take the definition "CPU = physical socket" but that
sounds incorrect for the aarch64 machines: do they really have 8 CPU
sockets as reported by lscpu?  Or is it just that each core has its own L3
cache so it can be considered to be an independent CPU?


[1] https://cfarm.tetaneutral.net/news/19
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