There was a bug in the openib btl handling this valid sequence of
calls:
desc = btl_alloc ();
btl_free (desc);
When triggered the bug would cause either fragment loss or undefined
behavior (SEGV, etc). The problem occured because btl_alloc contained
the logic to modify the pending fragment (length, etc) and these
changes were not corrected if the fragment was freed instead of sent.
To fix this issue I 1) moved some of the coalescing logic to the
btl_send function, and 2) retry the coalesced fragment on btl_free
if it was never sent. This appears to completely address the issue.
WHAT: Open our low-level communication infrastructure by moving all necessary components (btl/rcache/allocator/mpool) down in OPAL
All the components required for inter-process communications are currently deeply integrated in the OMPI layer. Several groups/institutions have express interest in having a more generic communication infrastructure, without all the OMPI layer dependencies. This communication layer should be made available at a different software level, available to all layers in the Open MPI software stack. As an example, our ORTE layer could replace the current OOB and instead use the BTL directly, gaining access to more reactive network interfaces than TCP. Similarly, external software libraries could take advantage of our highly optimized AM (active message) communication layer for their own purpose. UTK with support from Sandia, developped a version of Open MPI where the entire communication infrastucture has been moved down to OPAL (btl/rcache/allocator/mpool). Most of the moved components have been updated to match the new schema, with few exceptions (mainly BTLs where I have no way of compiling/testing them). Thus, the completion of this RFC is tied to being able to completing this move for all BTLs. For this we need help from the rest of the Open MPI community, especially those supporting some of the BTLs. A non-exhaustive list of BTLs that qualify here is: mx, portals4, scif, udapl, ugni, usnic.
This commit was SVN r32317.
