RE: NFSD generic R/W API (sendto path) performance results

["Steve Wise" <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>]

> 
> > On Nov 17, 2016, at 10:04 AM, Chuck Lever <chuck.lever-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org> wrote:
> >
> >> On Nov 17, 2016, at 7:46 AM, Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org> wrote:
> >> Also did you try to always register for > max_sge
> >> calls?  The code can already register all segments with the
> >> rdma_rw_force_mr module option, so it would only need a small tweak for
> >> that behavior.
> >
> > For various reasons I decided the design should build one WR chain for
> > each RDMA segment provided by the client. Good clients expose just
> > one RDMA segment for the whole NFS READ payload.
> >
> > Does force_mr make the generic API use FRWR with RDMA Write? I had
> > assumed it changed only the behavior with RDMA Read. I'll try that
> > too, if RDMA Write can easily be made to use FRWR.
> 
> Unfortunately, some RPC replies are formed from two or three
> discontiguous buffers. The gap test in ib_sg_to_pages returns
> a smaller number than sg_nents in this case, and rdma_rw_init_ctx
> fails.
> 
> Thus with my current prototype I'm not able to test with FRWR.
> 
> I could fix this in my prototype, but it would be nicer for me if
> rdma_rw_init_ctx handled this case the same for FRWR as it does
> for physical addressing, which doesn't seem to have any problem
> with a discontiguous SGL.

Just to make sure I'm understanding you, for rdma-rw to handle this,  it would
have to use multiple REG_MR registrations, one for each contiguous area in the
scatter list.  

Right?

--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html