superbench mpi job should use the proper Ethernet interface about superbenchmark HOT 2 CLOSED

When there're multiple Ethernet interfaces available, there won't be "default", OMPI will automatically detect the usable interface using its routability algorithm. The detection is complex and it still cannot cover some cases which require user to specify btl_tcp_if_include and btl_tcp_if_exclude explicitly.

You can pass through such parameters in config yaml:

modes:
- name: mpi
  mca:
    btl_tcp_if_include: azure2

For the proposed get_eth_interfaces detection, it cannot cover some scenarios as well and may not be better than current OMPI's detection. Here're two cases:

• "MPI job that spans public and private networks" that OMPI cannot cover, consider the following two nodes

  |    Node A     |     |    Node B     |
  |               |     |               |
  |     eth0      |     |     eth0      |    # public network, cannot route to each other
  | 192.168.100.1 |     | 192.168.100.2 |
  |               |     |               |
  |     eth1      |     |     eth1      |    # private network, can route to each other
  | 192.168.200.1 |     | 192.168.200.2 |
  

  eth0 is only used to access Internet and they cannot route to each other, while eth1 of two nodes are connected to the same switch in private networking. You detection method would think both of them are usable (ipv4, with ip, no bridge, not docker), it's hard to choose the correct one without extra knowledge for cluster networking.

• When all ethernet interfaces (azure2 and eth0 in your case) are disabled or unavailable, IPoIB can also be used for mpi, for example, changing to btl_tcp_if_include ib0 should also work in your environment. The get_eth_interfaces detection would also exclude suitable interfaces.

from superbenchmark.

will use one by setting the config file

from superbenchmark.