netdev - Re: Designing a safe RX-zero-copy Memory Model for Networking

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Message-ID: <alpine.DEB.2.20.1612141059020.20959@east.gentwo.org>
Date:   Wed, 14 Dec 2016 11:00:12 -0600 (CST)
From:   Christoph Lameter <cl@...ux.com>
To:     Hannes Frederic Sowa <hannes@...essinduktion.org>
cc:     Jesper Dangaard Brouer <brouer@...hat.com>,
        John Fastabend <john.fastabend@...il.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Björn Töpel <bjorn.topel@...el.com>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Tom Herbert <tom@...bertland.com>,
        Brenden Blanco <bblanco@...mgrid.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Kalman Meth <METH@...ibm.com>,
        Vladislav Yasevich <vyasevich@...il.com>
Subject: Re: Designing a safe RX-zero-copy Memory Model for Networking

On Tue, 13 Dec 2016, Hannes Frederic Sowa wrote:

> > Interesting.  So you even imagine sockets registering memory regions
> > with the NIC.  If we had a proper NIC HW filter API across the drivers,
> > to register the steering rule (like ibv_create_flow), this would be
> > doable, but we don't (DPDK actually have an interesting proposal[1])
>
> On a side note, this is what windows does with RIO ("registered I/O").
> Maybe you want to look at the API to get some ideas: allocating and
> pinning down memory in user space and registering that with sockets to
> get zero-copy IO.

Yup that is also what I think. Regarding the memory registration and flow
steering for user space RX/TX ring please look at the qpair model
implemented by the RDMA subsystem in the kernel. The memory semantics are
clearly established there and have been in use for more than a decade.