Re: [PATCH v2] RDMA/cma: Make CM response timeout and # CM retries configurable

Jason Gunthorpe
2019-06-13T23:46:37Z

On Thu, Jun 13, 2019 at 07:39:24PM +0200, Håkon Bugge wrote:
>
>
> > On 13 Jun 2019, at 19:23, Jason Gunthorpe <jgg@ziepe.ca> wrote:
> >
> > On Thu, Jun 13, 2019 at 06:58:30PM +0200, Håkon Bugge wrote:
> >
> >> If you refer to the backlog parameter in rdma_listen(), I cannot see
> >> it being used at all for IB.
> >>
> >> For CX-3, which is paravirtualized wrt. MAD packets, it is the proxy
> >> UD receive queue length for the PF driver that can be construed as a
> >> backlog.
> >
> > No, in IB you can drop UD packets if your RQ is full - so the proxy RQ
> > is really part of the overall RQ on QP1.
> >
> > The backlog starts once packets are taken off the RQ and begin the
> > connection accept processing.
>
> Do think we say the same thing. If, incoming REQ processing is
> severly delayed, the backlog is #entries in the QP1 receive queue in
> the PF. I can call rdma_listen() with a backlog of a zillion, but it
> will not help.

backlog and queue depth are different things, we shouldn't confuse
them together..

Jason