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Subject: [OMPI devel] RFC: Linuxes shipping libibverbs
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2008-05-21 10:02:51


What: Change default in openib BTL to not complain if no OpenFabrics
devices are found

Why: Many linuxes are shipping libibverbs these days, but most users
still don't have OpenFabrics hardware

Where: btl_openib_component.c

When: For v1.3

Timeout: Teleconf, 27 May 2008

Short version
=============

Many major linuxes are shipping libibverbs by default these days.
OMPI will therefore build the openib BTL by default, but then
complains at run time when there's no OpenFabrics hardware.

We should change the default in v1.3 to not complain if there is no
OpenFabrics devices found (perhaps have an MCA param to enable the
warning if desired).

Longer version
==============

I just got a request from the Debian Open MPI package maintainers to
include the following in the default openmpi-mca-params.conf for the
OMPI v1.2 package:

# Disable the use of InfiniBand
# btl = ^openib

Having this in the openmpi-mca-params.conf gives Debian an easy
documentation path for users to shut up these warnings when they build
on machines with libibverbs present but no OpenFabrics hardware.

I think that this is fine for the v1.2 series (and will file a CMR for
it). But for v1.3, I think we should change the default.

The vast majority of users will not have OpenFabrics devices, and we
should therefore not complain if we can't find any at run-time. We
can/should still complain if we find OpenFabrics devices but no active
ports (i.e., don't change this behavior).

But for optimizing the common case: I think we should (by default) not
print a warning if no OpenFabrics devices are found. We can also
[easily] have an MCA parameter that *will* display a warning if no
OpenFabrics devices are found.

-- 
Jeff Squyres
Cisco Systems