Re: [PATCH v4 01/14] svcrdma: Reduce the number of rdma_rw contexts per-QP

Jason Gunthorpe
2025-05-06T13:55:38Z

On Tue, May 06, 2025 at 06:40:25AM -0700, Christoph Hellwig wrote:
> On Tue, May 06, 2025 at 10:17:22AM -0300, Jason Gunthorpe wrote:
> > On Tue, May 06, 2025 at 06:08:59AM -0700, Christoph Hellwig wrote:
> > > On Mon, Apr 28, 2025 at 03:36:49PM -0400, cel@kernel.org wrote:
> > > > qp_attr.cap.max_rdma_ctxs. The QP's actual Send Queue length is on
> > > > the order of the sum of qp_attr.cap.max_send_wr and a factor times
> > > > qp_attr.cap.max_rdma_ctxs. The factor can be up to three, depending
> > > > on whether MR operations are required before RDMA Reads.
> > > >
> > > > This limit is not visible to RDMA consumers via dev->attrs. When the
> > > > limit is surpassed, QP creation fails with -ENOMEM. For example:
> > >
> > > Can we find a way to expose this limit from the HCA drivers and the
> > > RDMA core?
> >
> > Shouldn't it be max_qp_wr?
>
> Does that allow for arbitrary combination of different WRs?

I think it is supposed to be the maximum QP WR depth you can create..

A QP shouldn't behave differently depending on the WR operation, each
one takes one WR entry.

Chuck do you know differently?

Jason