On 12/19/2011 2:10 AM, V. Ram wrote:
On Thu, Dec 15, 2011, at 09:28 PM, Jeff Squyres wrote:
Very strange.  I have a lot of older mthca-based HCAs in my Cisco MPI
test cluster, and I don't see these kinds of problems.
Can I ask what version of OFED you're using, or what version of OFED the
IB software stack is coming from?

Just to set expectations here, Jeff is on vacation until January so he might not reply to this anytime soon.

Thank you.

V. Ram

On Dec 15, 2011, at 7:24 PM, V. Ram wrote:

Hi Terry,

Thanks so much for the response.  My replies are in-line below.

On Thu, Dec 15, 2011, at 07:00 AM, TERRY DONTJE wrote:
IIRC, RNR's are usually due to the receiving side not having a segment 
registered and ready to receive data on a QP.  The btl does go through a 
big dance and does its own flow control to make sure this doesn't happen.

So when this happens are both the sending and receiving nodes using 
mthca's to communicate with?
Yes.  For the newer nodes using onboard mlx4, this issue doesn't arise. 
The mlx4-based nodes are using the same core switch as the mthca nodes.

By any chance is it a particular node (or pair of nodes) this seems to 
happen with?
No.  I've got 40 nodes total with this hardware configuration, and the
problem has been seen on most/all nodes at one time or another.  It
doesn't seem, based on the limited number of observable parameters I'm
aware of, to be dependent on the number of nodes involved.

It is an intermittent problem, but when it happens, it happens at job
launch, and it does occur most of the time.


V. Ram

Open MPI InfiniBand gurus and/or Mellanox: could I please get some
assistance with this? Any suggestions on tunables or debugging
parameters to try?

Thank you very much.

On Mon, Dec 12, 2011, at 10:42 AM, V. Ram wrote:

We are running a cluster that has a good number of older nodes with
Mellanox IB HCAs that have the "mthca" device name ("ib_mthca" kernel

These adapters are all at firmware level 4.8.917 .

The Open MPI in use is 1.5.3 , kernel 2.6.39 , x86-64. Jobs are
launched/managed using Slurm 2.2.7. The IB software and drivers
correspond to OFED , and I've verified that the kernel modules
in use are all from this OFED version.

On nodes with the mthca hardware *only*, we get frequent, but
intermittent job startup failures, with messages like:


[[19373,1],54][btl_openib_component.c:3320:handle_wc] from compute-c3-07
to: compute-c3-01 error polling LP CQ with status RECEIVER NOT READY
number 13 for wr_id 2a25c200 opcode 128 vendor error 135 qp_idx 0

The OpenFabrics "receiver not ready" retry count on a per-peer
connection between two MPI processes has been exceeded. In general,
this should not happen because Open MPI uses flow control on per-peer
connections to ensure that receivers are always ready when data is

[further standard error text snipped...]

Below is some information about the host that raised the error and the
peer to which it was connected:

Local host: compute-c3-07
Local device: mthca0
Peer host: compute-c3-01

You may need to consult with your system administrator to get this
problem fixed.


During these job runs, I have monitored the InfiniBand performance
counters on the endpoints and switch. No telltale counters for any of
these ports change during these failed job initiations.

ibdiagnet works fine and properly enumerates the fabric and related
performance counters, both from the affected nodes, as well as other
nodes attached to the IB switch. The IB connectivity itself seems fine
from these nodes.

Other nodes with different HCAs use the same InfiniBand fabric
continuously without any issue, so I don't think it's the fabric/switch.

I'm at a loss for what to do next to try and find the root cause of the
issue. I suspect something perhaps having to do with the mthca
support/drivers, but how can I track this down further?

Thank you,

V. Ram.
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Terry D. Dontje | Principal Software Engineer
Developer Tools Engineering | +1.781.442.2631
Oracle - Performance Technologies
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Email terry.dontje@oracle.com