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DMA related RAS events APPL_0A2B and APPL_0201 --> improve communication performance

When using the option -verbose 2 with the mpirun command users might find information about the RAS events APPL_0A2B and/or APPL_0201 in the stderr. These events are not critical (i.e. the application does not fail). However, the performance might be not optimal.

APPL_0A2B - A DMA unit reception FIFO is full

Packets that arrive off the network are placed into a reception buffer. The default size is 8 MB per process. If a process is busy and does not call MPI_Wait often enough, this buffer can become full and the movement of further packets is stopped until the buffer is free again. This can slow down the application. In this case the buffer should be increased to the value given in the RAS event message using the environment variable DCMF_RECFIFO (see Tuning Applications for further information).

APPL_0201 - A DMA unit remote get injection FIFO is full

When a remote get packet arrives off the network, the packet contains a descriptor describing data that is to be retrieved and sent back to the node that originated the remote get packet. The DMA injects that descriptor into a remote get injection buffer. The DMA then processes that injected descriptor by sending the data back to the originating node. Remote gets are commonly done during point-to-point communications when large data buffers are involved (typically larger than 1200 bytes). The default size of the remote get injection FIFO is 32 KB. When a large number of remote get packets are received by a node, the remote get injection buffer may become full of descriptors. The size of the buffer can be adjusted to the value given in the RAS event message using the environment variable DCMF_RGETFIFO (see Tuning Applications for further information).


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