Open MPI IB Gurus, I have some slightly older InfiniBand-equipped nodes with IB which have less RAM than we'd like, and on which we tend to run jobs that can span 16-32 nodes of this type. The jobs themselves tend to run on the heavy side in terms of their own memory requirements.
When we used to run on an older Intel MPI, these jobs managed to run within the available RAM without paging out to disk. Now using Open MPI 1.5.3, we can end up paging to disk or even running out of memory for the same codes and exact same jobs and node distributions. I'm suspecting that I can reduce overall memory consumption by tuning the IB-related memory that Open MPI consumes. I've looked at the FAQ: http://www.open-mpi.org/faq/?category=openfabrics#limiting-registered-memory-usage , but I'm still not certain about where I should start. Again, this is all for 1.5.3 (we are willing to update to 1.5.4 or 1.5.5 when released, if it would help). 1. It looks like there are several independent IB BTL MCA parameters to try adjusting: i. mpool_rdma_rcache_size_limit, ii. btl_openib_free_list_max , iii. btl_openib_max_send_size , iv. btl_openib_eager_rdma_num, v. btl_openib_max_eager_rdma, vi. btl_openib_eager_limit . Have I missed any others parameters that impact InfiniBand-related memory usage? These parameters are listed as affecting registered memory. Are there parameters that affect unregistered IB-related memory consumption on the part of Open MPI itself? 2. Where should I start with this? For example, is it worth trying to adjust any of the eager parameters, or are the bulk of the memory requirements coming from the mpool_rdma_rcache_size_limit? 3. Are there any gross/overall "master" parameters that will set limits, but keep the various buffers in intelligent proportion to one another, or will I need to manually adjust each set of buffers independently? If the latter, are there any guidelines on the relative proportions between buffers, or overall recommendations? Thank you very much. -- http://www.fastmail.fm - A fast, anti-spam email service.
