[ofw] post send in kernel mode

[Sujatha Tolstoy]

Supporting it on w2k8 (and beyond) OSes should be ok if there are clear 
constraints supporting it on w2k3...

Like you said, Idea of a split model is to make use of rdmacm which is only in user mode today.

regards
Sujatha


Sean Hefty wrote:
>> I wish to discuss yet another option for RDS protocol:
>> Connection establishment in user mode (use of the rdma_cm over Winverbs)
>> and data xfer in kernel mode using post send operation.
>>
>> Basically QP and CQ can be obtained in kernel mode winverbs driver
>> using WvQpAcquire(..) and WvCqAcquire() respectively.
>> And post_send and poll_cq done using HCA verbs interface calls
>> QP->pVerbs->post_send() and QP->pVerbs->poll_cq().
>>
>> Please let me know this kernel mode option for data xfer is feasible or
>> am  I missing anything here.
>>     
>
> I think the only functionality that's needed from userspace is the equivalent
> rdma_resolve_addr/rdma_resolve_route.  (We kind of keep coming back to this.)
> The actual connection could still be done in the kernel.
>
> The basic way the stack works today is that librdmacm performs the address and
> route resolution.  It then makes a 'Modify' call into the winverbs library to
> set the address and path information, which sets the kernel data structures.
> Not exactly ideal, but I don't know that this can cause any real harm.
>
> If you're looking at a split model, then I would limit what's required from
> userspace to obtaining the information.  Everything else should be doable from
> the kernel.  This kind of gets us back to what in userspace provides the
> information and through what sort of interface.
>
> I guess a question to ask is would supporting this on 2008+ be enough?
>
> - Sean
>
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