Roland thought that the default value of 10 might be a bit too low and
that tuning it to be higher, particularly in apps that pound on a
single port, would probably be acceptable.
Tuning up to 20 is probably a bit overkill.
On Nov 27, 2007, at 3:54 PM, Jeff Squyres wrote:
BTW, Andrew is correct about the unit for btl_openib_ib_timeout and
that the value is simply passed down to the verbs library when
making an IB connection. Open MPI does nothing else with that
value; it's an IBTA-defined value.
The help message was wrong on the 1.2 branch for a while; I think
it's been corrected in more recent versions of OMPI (i.e., >1.2 -- I
don't recall which version specifically).
On Nov 27, 2007, at 3:19 PM, Andrew Friedley wrote:
Brock Palen wrote:
What would be a place to look? Should this just be default then
for
OMPI? ompi_info shows the default as 10 seconds? Is that right
'seconds' ?
The other IB guys can probably answer better than I can -- I'm
not an
expert in this part of IB (or really any part I guess :). Not sure
why
a larger value isn't the default. No, its not seconds -- check the
description of the MCA parameter:
4.096 microseconds * (2^btl_openib_ib_timeout)
You sure?
ompi_info --param btl openib
MCA btl: parameter "btl_openib_ib_timeout" (current value: "10")
InfiniBand transmit timeout, in seconds
(must be >= 1)
Yeah:
MCA btl: parameter "btl_openib_ib_timeout" (current value: "10")
InfiniBand transmit timeout, plugged into formula:
4.096 microseconds * (2^btl_openib_ib_timeout)(must be
= 0 and <= 31)
Reading earlier in the thread you said OMPI v1.2.0, I got this from a
trunk checkout thats around 3 weeks old. A quick check shows this
description was changed between 1.2.0 and 1.2.1. However the use of
this parameter hasn't changed -- it's simply passed along to IB verbs
when creating a queue pair (aka a connection).
Andrew
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Jeff Squyres
Cisco Systems
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Jeff Squyres
Cisco Systems
