[mvapich-discuss] mvapich2-0.9.8-branch question

[Kanoj Sarcar]

Hello all,

I am a mpi/mvapich newbie looking at iwarp support in
mvapich2.

Between 0.9.8 release and branch, in procedure
rdma_get_control_parameters() in file
src/mpid/osu_ch3/channels/mrail/src/gen2/ibv_param.c,
I see a difference that I am trying to understand.

In the release version, the code was:

   if ((value = getenv("MV2_DISABLE_RDMA_FAST_PATH"))
!= NULL) {
        proc->has_adaptive_fast_path = 0;
        rdma_polling_set_limit       = 0;
    } else {
        proc->has_adaptive_fast_path = 1;
    }

but this got changed in the branch version to also
turn off adaptive fast path in case of iwarp. 

I am curious about the rationale for this change. Is
this to mostly support amasso card that (AFAIK) does
not have user mode fastpath support? Or is there some
architectural issue in current mvapich2 that requires
turning off fastpath on iwarp rnics?

Thanks. 

Kanoj

PS: please cc me on responses, I am not subscribed to
the list


 
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