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Subject: [OMPI users] Role of ethernet interfaces of startup of openmpi job using IB
From: Salvatore Podda (salvatore.podda_at_[hidden])
Date: 2011-09-27 06:35:05


Dear all,

        We would like to know if the ethernet interfaces play any role in the
startup phase of an opempi job using InfiniBand
  In this case, where we can found some literature on this topic?

This interest arises from some observations of a substantial time
overhead on the startup of our openmpi jobs using IB.
Looking at the `tcpdump' on the involved nodes we register a
substained ARP traffic on the eth0/eth1 interfaces on the
nodes itself. Following the suggestions on

http://www.openfabrics.org/downloads/OFED/ofed-1.4/OFED-1.4-docs/ipoib_release_notes.txt

we filter the arp traffic on both the eth interfaces obtainig a
drammatic reduction on the time overhead.
This depends also from the eth interface we decide to filter. We do
realize to have some trouble
in our ethernet fabric and for a better understanding of the problems
we would to know the role, if any,
of the eth interfaces.

Regards

Salvatore Podda

ENEA UTICT-HPC
Department for Computer Science Development and ICT
Facilities Laboratory for Science and High Performace Computing

C.R. Frascati
Via E. Fermi, 45
PoBox 65
00044 Frascati (Rome)
Italy

Tel: +39 06 9400 5342
Fax: +39 06 9400 5551
Fax: +39 06 9400 5735
E-mail: salvatore.podda_at_[hidden]
Home Page: www.cresco.enea.it