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Subject: Re: [OMPI devel] RGET issue when send is less than receive
From: Nathan Hjelm (hjelmn_at_[hidden])
Date: 2013-06-21 11:40:09


I thought I fixed this problem awhile back (though looking at the code its possible I never committed the fix). I will have to look through my local repository and see what happened to that fix. Your fix might not work correctly since a RGET can be broken up into multiple get operations. It may work, I would just need to test it to make sure.

-Nathan

On Fri, Jun 21, 2013 at 08:25:29AM -0700, Rolf vandeVaart wrote:
> I ran into a hang in a test in which the sender sends less data than the receiver is expecting. For example, the following shows the receiver expecting twice what the sender is sending.
>
> Rank 0: MPI_Send(buf, BUFSIZE, MPI_INT, 1, 99, MPI_COMM_WORLD)
> Rank 1: MPI_Recv(buf, BUFSIZE*2, MPI_INT, 0, 99, MPI_COMM_WORLD)
>
> This is also reproducible using one of the intel tests and adjusting the eager value for the openib BTL.
>
> ? mpirun -np 2 -host frick,frack -mca btl_openib_eager_limit 56 MPI_Send_overtake_c
>
> In most cases, this works just fine. However, when the PML protocol used is the RGET protocol, the test hangs. Below is a proposed fix for this issue.
> I believe we want to be checking against req_bytes_packed rather than req_bytes_expected as req_bytes_expected is what the user originally told us.
> Otherwise, with the current code, we never send a FIN message back to the sender.
>
> Any thoughts?
>
> [rvandevaart_at_sm065 ompi-trunk]$ svn diff ompi/mca/pml/ob1/pml_ob1_recvreq.c
> Index: ompi/mca/pml/ob1/pml_ob1_recvreq.c
> ===================================================================
> --- ompi/mca/pml/ob1/pml_ob1_recvreq.c (revision 28633)
> +++ ompi/mca/pml/ob1/pml_ob1_recvreq.c (working copy)
> @@ -335,7 +335,7 @@
> /* is receive request complete */
> OPAL_THREAD_ADD_SIZE_T(&recvreq->req_bytes_received, frag->rdma_length);
> - if (recvreq->req_bytes_expected <= recvreq->req_bytes_received) {
> + if (recvreq->req_recv.req_bytes_packed <= recvreq->req_bytes_received) {
> mca_pml_ob1_send_fin(recvreq->req_recv.req_base.req_proc,
> bml_btl,
> frag->rdma_hdr.hdr_rget.hdr_des,
>
>
>
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