[openib-general] Mellanox HCAs: outstanding RDMAs

[somenath]

What happens if one tries to do RDMA (say write for example) higher than
4 (or 128 in changed case)? does it just wait till previos operation is 
completed?
 I don't remember seeing any error ....it was only
limited by the send Q-depth which can go much larger value.

thanks, som.

Roland Dreier wrote:

>    Manpreet> Mellanox HCA can handle has been configured at 4
>    Manpreet> (mthca_main.c: default_profile: rdb_per_qp). And the
>    Manpreet> HCAs can support a much higher value (128 I think).
>
>    Manpreet> Could we move this value higher or atleast make it
>    Manpreet> configurable?
>
>Leonid Arsh has a patch that I will integrate soon that makes this
>configurable.
>
>However, I'm curious.  Do you have a workload where this actually
>makes a measurable difference?  It seems that having 4 RDMA requests
>outstanding on the wire should be enough to get things to pipeline
>pretty well.
>
>If you haven't tested this, right now you can of course edit
>mthca_main.c to change the default value and recompile.
>
> - R.
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