[mvapich-discuss] Suppressing send work request completions in RNDV RDMA_WRITE

[Hari Subramoni]

Hello Jagadeesh,

MVAPICH2 uses pre-registered memory regions to post data to QPs. MVAPICH2
requests for completion events so that these regions can be recovered after
the WQE has been completed

Regards,
Hari.

On Tue, Oct 14, 2014 at 8:57 AM, Pagadala Jagadeesh <pjagadeesh at cdac.in>
wrote:

>   Hi all,
>
>  I am trying to understand RNDV protocol in MVAPICH2-1.9 with respect to
> RDMA_WRITE operation.
>  For data size of more than 4MB, each RDMA_WRITE request carries 4M
> data and all such send work requests are generating completion entry.
>  In InfiniBand there is a mechanism to suppress send completion entries(
> MVAPICH2-1.9 is enabling this feature when creating a QP using
> attr.sq_sig_all = 0,
> But not using send completion suppression while posting send work
> request).
> In case of RDMA_WRITE (RNDV) we can suppress intermediate send
> completions,
> when last send request completion is generated then we can make sure that
> previous send work requests are also completed successfully.
>
> Is there any overhead of suppressing such intermediate send completions?
>
>  Thanks & Regards
>  Jagadeesh
>
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