Hello,
while currently only supported by the InfiniBand transport,
the libibverbs define a IBV_WR_RDMA_WRITE_WITH_IMM work request.
Could someone please explain what the action at the peer side would be
if a WRITE with immediate data comes in? One possible action would be
to:
(1) fetch the next receive queue / shared receive queue entry and
store the value of the immediate data (32 bits at the API)
along with that RQE.
(2) place data according to the inbound WRITE hdr but ignore the
SGL of the RQE.
(3) after completion processing the WRITE:
(1) create a work completion of type IBV_WC_RECV_RDMA_WITH_IMM,
(2) transfer the immediate data value into the 'imm_data' field,
(3) set the WC's 'byte_len' to the received WRITE payload,
(4) set IBV_WC_WITH_IMM at 'wc_flags', and
(5) append the WC to the associated CQ.
With that, the receiver would have to carefully inspect the operation
type of the work completion, since a receive queue entry may turn into
a IBV_WC_RECV or IBV_WC_RECV_RDMA_WITH_IMM. In the second case, the data
are placed according to the senders opinion, which may not be the
result a non-aware receiver would expect.
correct?
Many thanks for clarification!
Bernard.
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