Hi,
for quite a long time already, there is a confusing inconsistency of the
description of the OpenIB parameters related to eager messages on this
FAQ site (see details below):
http://www.open-mpi.org/faq/?category=openfabrics
Does somebody here has the necessary permissions to fix this?
The answer to question 20 says (last row in the table):
"Each MPI process will use RDMA buffers for eager fragments up to
btl_openib_eager_rdma_num MPI peers. Upon receiving the
btl_openib_eager_rdma_threshhold'th message from an MPI peer process, if
both sides have not yet setup btl_openib_eager_rdma_num sets of eager
RDMA buffers, a new set will be created. The set will contain
btl_openib_max_eager_rdma buffers; each buffer will be
btl_openib_eager_limit bytes (i.e., the maximum size of an eager
fragment)."
while part of the answer of question 24 says the following:
* btl_openib_max_eager_rdma (default value: 16): This parameter
controls the maximum number of peers that can receive and RDMA
connection for short messages. It is not advisable to change this
value to a very large number because the polling time increase with
the number of the connections; as a direct result, short message
latency will increase.
* btl_openib_eager_rdma_num (default value: 16): This parameter
controls the maximum number of pre-allocated buffers allocated to
each peer for small messages.
- Lars
--
Lars Schaefers
Computer Engineering Group of Prof. Dr. Marco Platzner
Paderborn Center for Parallel Computing, University of Paderborn
Pohlweg 47-49, 33098 Paderborn, Germany
Tel: +49 (0)5251 60 4341, Fax: +49 (0)5251 60 5377
Office: Building O 3.119
