Paul I tried NetPipeMPI - (belatedly because their site was down down for a couple of days)

The results show a max of 7.4 Gb/s at 8388605 bytes which seems fine.

But my program still runs slowly and stalls occasionally.
I've using 1 buffer per process - I assume this is ok.
Is it of any significance that the  log_num_mtt and log_mtts_per_seg params where not set?
Is this a symptom of a broken install?

Reposting original message for clarity - its been a few days...
2nd posts are below this 1st section
========================================================================================
I have a test rig comprising 2 i7 systems 8GB RAM with Melanox III HCA 10G cards
running Centos 5.7 Kernel 2.6.18-274
Open MPI 1.4.3
MLNX_OFED_LINUX-1.5.3-1.0.0.2 (OFED-1.5.3-1.0.0.2):
On a Cisco 24 pt switch

Normal performance is:
$ mpirun --mca btl openib,self -n 2 -hostfile mpi.hosts  PingPong
results in:
 Max rate = 958.388867 MB/sec  Min latency = 4.529953 usec
and:
$ mpirun --mca btl tcp,self -n 2 -hostfile mpi.hosts  PingPong
Max rate = 653.547293 MB/sec  Min latency = 19.550323 usec


My application exchanges about a gig of data between the processes with 2 sender and 2 consumer processes on each node with 1 additional controler process on the starting node.
The program splits the data into 64K blocks and uses non blocking sends and receives with busy/sleep loops to monitor progress until completion.

My problem is I see better performance under IPoIB then I do on native IB (RDMA_CM).
My understanding is that IPoIB is limited to about 1G/s so I am at a loss to know why it is faster.

These 2 configurations are equivelant (about 8-10 seconds per cycle)
mpirun --mca btl_openib_flags 2 --mca mpi_leave_pinned 1 --mca btl tcp,self -H vh2,vh1 -np 9 --bycore prog
mpirun --mca btl_openib_flags 3 --mca mpi_leave_pinned 1 --mca btl tcp,self -H vh2,vh1 -np 9 --bycore prog

And this one produces similar run times but seems to degrade with repeated cycles:
mpirun --mca btl_openib_eager_limit 64 --mca mpi_leave_pinned 1 --mca btl openib,self -H vh2,vh1 -np 9 --bycore  prog

Other  btl_openib_flags settings result in much lower performance. 
Changing the first of the above configs to use openIB results in a 21 second run time at best.  Sometimes it takes up to 5 minutes.
With openib:
- Repeated cycles during a single run seem to slow down with each cycle.
- On occasions it seems to stall indefinately, waiting on a single receive. 

Any ideas appreciated.

Thanks in advance,
Randolph


From: Randolph Pullen <randolph_pullen@yahoo.com.au>
To: Paul Kapinos <kapinos@rz.rwth-aachen.de>; Open MPI Users <users@open-mpi.org>
Sent: Thursday, 30 August 2012 11:46 AM
Subject: Re: [OMPI users] Infiniband performance Problem and stalling

Interesting, the log_num_mtt and log_mtts_per_seg params where not set.
Setting them to utilise 2*8G of my RAM resulted in no change to the stalls or run time ie; (19,3) (20,2) (21,1) or (6,16). 
In all cases, OpenIB runs in twice the time it takes TCP,except if I push the small message max to 64K and force short messages.  Then the openib times are the same as TCP and no faster.

I'ms till at a loss as to why...


From: Paul Kapinos <kapinos@rz.rwth-aachen.de>
To: Randolph Pullen <randolph_pullen@yahoo.com.au>; Open MPI Users <users@open-mpi.org>
Sent: Tuesday, 28 August 2012 6:13 PM
Subject: Re: [OMPI users] Infiniband performance Problem and stalling

Randolph,
after reading this:

On 08/28/12 04:26, Randolph Pullen wrote:
> - On occasions it seems to stall indefinately, waiting on a single receive.

... I would make a blind guess: are you aware about IB card parameters for registered memory?
http://www.open-mpi.org/faq/?category=openfabrics#ib-low-reg-mem

"Waiting forever" for a single operation is one of symptoms of the problem especially in 1.5.3.


best,
Paul

P.S. the lower performance with 'big' chinks is known phenomenon, cf.
http://www.scl.ameslab.gov/netpipe/
(image on bottom of the page). But the chunk size of 64k is fairly small




-- Dipl.-Inform. Paul Kapinos  -  High Performance Computing,
RWTH Aachen University, Center for Computing and Communication
Seffenter Weg 23,  D 52074  Aachen (Germany)
Tel: +49 241/80-24915




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