[openib-general] Re: Mellanox HCAs: outstanding RDMAs

[Michael S. Tsirkin]

Quoting r. Talpey, Thomas <Thomas.Talpey at netapp.com>:
> Subject: Re: Mellanox HCAs: outstanding RDMAs
> 
> At 03:43 AM 6/6/2006, Michael S. Tsirkin wrote:
> >Quoting r. Talpey, Thomas <Thomas.Talpey at netapp.com>:
> >> Semantically, the provider is not required to provide any such flow control
> >> behavior by the way. The Mellanox one apparently does, but it is not
> >> a requirement of the verbs, it's a requirement on the upper layer. If more
> >> RDMA Reads are posted than the remote peer supports, the connection
> >> may break.
> >
> >This does not sound right. Isn't this the meaning of this field:
> >"Initiator Depth: Number of RDMA Reads & atomic operations
> >outstanding at any time"? Shouldn't any provider enforce this limit?
> 
> The core spec does not require it. An implementation *may* enforce it,
> but is not *required* to do so. And as pointed out in the other message,
> there are repercussions of doing so.

Interesting, I wasn't aware of such interpretation of the spec.
When QP is modified to RTS, the initiator depth is passed to it, which
suggests that the provider must obey, not ignore this parameter. No?

-- 
MST