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Subject: Re: [OMPI devel] RGET issue when send is less than receive
From: Jeff Squyres (jsquyres) (jsquyres_at_[hidden])
Date: 2013-06-21 13:18:16


Does this need to go to v1.6?

On Jun 21, 2013, at 11:59 AM, Nathan Hjelm <hjelmn_at_[hidden]> wrote:

> Found my original fix (still don't know why I never pushed it) and I think George is correct. This should in both the single and multiple get cases.
>
> -Nathan
>
> On Fri, Jun 21, 2013 at 05:52:28PM +0200, George Bosilca wrote:
>> The amount of bytes received is atomically updated on the completion callback, and the completion test is clearly spelled-out int the recv_request_pml_complete_check function (of course minus the lock part). Rolf I think your patch is correct.
>>
>> That being said req_bytes_expected is a special value, one that should only be used to check from truncation. Otherwise, req_bytes_packed is the value we should compare against.
>>
>> George.
>>
>> On Jun 21, 2013, at 17:40 , Nathan Hjelm <hjelmn_at_[hidden]> wrote:
>>
>>> 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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-- 
Jeff Squyres
jsquyres_at_[hidden]
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