On Fri, 20 Jul 2012 13:50:19 -0400
Hal Rosenstock <[email protected]> wrote:
> Hi Susan,
>
> On 7/20/2012 1:30 PM, Susan Coulter wrote:
> > Question:
> > About 2 years ago I reported at the OFA Developers Workshop that the ecmp
> > routing within MinHop does not equally distribute routes among the multiple
> > paths. That is, if 4 different ports at one hop all result in an equal
> > number of hops thru the rest of the fabric, the routes are not distributed
> > equally among those 4 ports/paths.
> >
> > I was told there were 2 different approaches to solve this and patches had
> > been discussed/submitted and the community was deciding on a path forward.
> >
> > Does anyone know the status of this?
>
> The two approaches are:
> 1. Scatter ports (from Jared Carr)
> 2. Port shifting (from Al Chu)
To turn these options on:
In opensm.conf:
# Assign ports in a random order instead of round-robin.
# If zero disable, otherwise use the value as a random seed
scatter_ports 0
# Port Shifting (use FALSE if unsure)
port_shifting FALSE
On the command line:
--scatter-ports
This option will randomize port selecting in routing.
--port-shifting
This option enables a feature called port shifting. In some
fabrics, particularly cluster environments, routes commonly align and congest
with other routes due to algorithmically unchanging traf-
fic patterns. This routing option will "shift" routing around in
an attempt to alleviate this problem.
Ira
>
> and both have been upstream since April 2011.
>
> -- Hal
>
> > My apologies if the data is out there somewhere and I simply cannot find it.
> >
> > Thanx in advance.
> >
> >
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> >
>
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--
Ira Weiny
Member of Technical Staff
Lawrence Livermore National Lab
925-423-8008
[email protected]
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