Small messages, i.e. their length is under btl_sm_eager_limit, always use normal SM. KNEM usage is restricted only for messages over either the eager size or the btl_sm_knem_dma_min (if KNEM supports DMA).


On Sep 4, 2013, at 12:47 , Alina Sklarevich <> wrote:


I am building ompi v1.6 with knem support and I see that when knem is enabed from the command line 
it is used for all message sizes in SM btl. There is no threshold for when to start using knem - starting 
which message size.
This makes the performance of small messages worse since it also uses knem.
Maybe a certain "knem threshold" should be added to specify when to use SM btl's send and when to start using knem.

What do you think?

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