On 6/23/2021 7:33 PM, Stephen Hemminger wrote: > On Wed, 23 Jun 2021 18:31:42 +0100 > Ferruh Yigit <ferruh.yi...@intel.com> wrote: > >> Add a note that KNI kernel module will be moved to dpdk-kmods git repo >> and there is a long term plan to deprecate it. >> >> Also add some more details on the alternatives to KNI and cons of the >> KNI against these alternatives. >> >> Signed-off-by: Ferruh Yigit <ferruh.yi...@intel.com> >> --- >> doc/guides/nics/tap.rst | 2 + >> .../prog_guide/kernel_nic_interface.rst | 38 +++++++++++++++++-- >> 2 files changed, 37 insertions(+), 3 deletions(-) >> >> diff --git a/doc/guides/nics/tap.rst b/doc/guides/nics/tap.rst >> index 3ce696b605d1..07315fe32422 100644 >> --- a/doc/guides/nics/tap.rst >> +++ b/doc/guides/nics/tap.rst >> @@ -1,6 +1,8 @@ >> .. SPDX-License-Identifier: BSD-3-Clause >> Copyright(c) 2016 Intel Corporation. >> >> +.. _TunTap_PMD: >> + >> Tun|Tap Poll Mode Driver >> ======================== >> >> diff --git a/doc/guides/prog_guide/kernel_nic_interface.rst >> b/doc/guides/prog_guide/kernel_nic_interface.rst >> index 1ce03ec1a374..29f8c92fd9d6 100644 >> --- a/doc/guides/prog_guide/kernel_nic_interface.rst >> +++ b/doc/guides/prog_guide/kernel_nic_interface.rst >> @@ -6,16 +6,48 @@ >> Kernel NIC Interface >> ==================== >> >> +.. Note:: >> + >> + KNI kernel module will be removed from main git repository to >> `dpdk-kmods <https://git.dpdk.org/dpdk-kmods/>`_ >> + repository by the `DPDK technical board decision >> <https://mails.dpdk.org/archives/dev/2021-January/197077.html>`_. >> + Also there is a `long term plan >> <https://mails.dpdk.org/archives/dev/2021-May/209026.html>`_ to deprecate >> the KNI. >> + >> + :ref:`virtio_user_as_exceptional_path` alternative is preferred way for >> + interfacing with Linux network stack as it is being in-kernel solution >> and >> + similar performance expectations. >> + >> The DPDK Kernel NIC Interface (KNI) allows userspace applications access to >> the Linux* control plane. >> >> -The benefits of using the DPDK KNI are: >> +KNI allows an interface with the kernel network stack and allows management >> of >> +DPDK ports using standard Linux net tools such as ``ethtool``, ``ifconfig`` >> and >> +``tcpdump``. >> + >> +Main use case of KNI is get/receive exception packets from/to Linux network >> +stack while main datapath IO is done bypassing the networking stack. >> + >> +There are other alternatives to KNI, all are available in the upstream >> Linux: >> + >> +#. :ref:`TunTap_PMD` as wrapper to `Linux tun/tap >> + <https://www.kernel.org/doc/Documentation/networking/tuntap.txt>`_ >> + >> +#. :ref:`virtio_user_as_exceptional_path` >> + >> +The benefits of using the DPDK KNI against alternatives are: >> >> * Faster than existing Linux TUN/TAP interfaces >> (by eliminating system calls and copy_to_user()/copy_from_user() >> operations. >> >> -* Allows management of DPDK ports using standard Linux net tools such as >> ethtool, ifconfig and tcpdump. >> +The cons of the DPDK KNI are: >> + >> +* It is out-of-tree Linux kernel module and it can't be distributed as >> binary as >> + part of OSV DPDK packages. This makes it harder to consume, although it is >> + always possible to compile it from the source code. >> + >> +* As it shares memory between userspace and kernelspace, and kernel part >> + directly uses input provided by userspace, it is not safe. This makes >> hard to >> + upstream the module. >> >> -* Allows an interface with the kernel network stack. >> +* Only a subset of control commands are supported by KNI. >> >> The components of an application using the DPDK Kernel NIC Interface are >> shown in :numref:`figure_kernel_nic_intf`. >> > > You should also link to virtio user as exception path. In my testing virtio > is as fast as KNI and uses less CPU. >
Patch mentions from virtio-user alternative, and in the notes it even documents it as preferred way.