Re: iblinkinfo for Python

[Benjamin Drung <benjamin.drung@ionos.com>]

Am Mittwoch, dem 05.01.2022 um 13:52 +0200 schrieb Leon Romanovsky:
> On Wed, Jan 05, 2022 at 11:32:40AM +0100, Benjamin Drung wrote:
> > Hi,
> > 
> > we have an in-house Shell script that uses iblinkinfo to check if the
> > InfiniBand cabling is correct. This information can be derived from
> > the
> > node names that can be seen for the HCA port. I want to improve that
> > check and rewrite it in Python, but I failed to find an easy and
> > robust
> > way to retrieve the node names for a HCA port:
> > 
> > 1) Call "iblinkinfo --line" and parse the output. Parsing the output
> > could probably be done with a complex regular expression. This
> > solution
> > is too ugly IMO.
> > 
> > 2) Extend iblinkinfo to provide a JSON output. Then let the Python
> > script call "iblinkinfo --json" and simply use json.load for parsing.
> > This solution requires some C coding and probably a good json library
> > should be used to avoid generating bogus JSON.
> > 
> > 3) Use https://github.com/jgunthorpe/python-rdma but this library has
> > not been touched for five years and needs porting to Python 3. So
> > that
> > is probably a lot of work as well.
> > 
> > 4) Use pyverbs provided by rdma-core, but I found neither a single
> > API
> > call to query similar data to iblinkinfo, nor an example for that use
> > case.
> > 
> > What should I do?
> 
> Isn't this information available in sysfs?
> [leonro@mtl-leonro-l-vm ~]$ cat /sys/class/infiniband/ibp0s9/node_desc
> mtl-leonro-l-vm ibp0s9

The host names of the nodes connected to this port are required for
this check, not the host name of the host itself.

> Can you give an example?

```
$ sudo iblinkinfo -y 1 -C mlx5_0 -P 0 --line
0x04400C64D87A2543 "                  host1 mlx5_0"     13    [...]
0x04400C64D87A255c "                  host2 mlx5_0"     10    [...]
[...]
```

iblinkinfo would return the host names of all connected hosts (in this
example snippet "host1" and "host2"). In our inhouse case, we can
derive the topology from these host names.
> 

-- 
Benjamin Drung

Senior DevOps Engineer and Debian & Ubuntu Developer
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