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From: Stephen Hemminger <stephen@networkplumber.org>
To: Ferruh Yigit <ferruh.yigit@intel.com>
Cc: dev@dpdk.org, Keith Wiles <keith.wiles@intel.com>,
	Thomas Monjalon <thomas@monjalon.net>
Subject: Re: [dpdk-dev] [PATCH] doc: note KNI alternatives and deprecation plan
Date: Wed, 23 Jun 2021 11:33:25 -0700	[thread overview]
Message-ID: <20210623113325.7687788f@hermes.local> (raw)
In-Reply-To: <20210623173142.3803801-1-ferruh.yigit@intel.com>

On Wed, 23 Jun 2021 18:31:42 +0100
Ferruh Yigit <ferruh.yigit@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.yigit@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.

  reply	other threads:[~2021-06-23 18:33 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-23 17:31 Ferruh Yigit
2021-06-23 18:33 ` Stephen Hemminger [this message]
2021-06-24  8:19   ` Ferruh Yigit
2021-07-30 12:48 ` Olivier Matz
2021-11-23 10:21   ` Ferruh Yigit
2021-08-20 12:58 ` David Marchand
2021-11-23 10:42   ` Ferruh Yigit
2021-11-23 12:08 ` [PATCH v2 1/2] doc: note KNI alternatives Ferruh Yigit
2021-11-23 12:08   ` [PATCH v2 2/2] doc: announce KNI deprecation Ferruh Yigit
2021-11-24 14:00     ` Thomas Monjalon
2021-11-24 13:58   ` [PATCH v2 1/2] doc: note KNI alternatives Thomas Monjalon
2021-11-24 14:19     ` Ferruh Yigit
2021-11-24 17:16 ` [PATCH v3 " Ferruh Yigit
2021-11-24 17:16   ` [PATCH v3 2/2] doc: announce KNI deprecation Ferruh Yigit
2022-07-11 14:47     ` Jerin Jacob
2022-07-13 10:01     ` Thomas Monjalon
2022-07-13 11:01       ` Bruce Richardson
2022-07-13 16:10     ` [PATCH v4] " Thomas Monjalon
2022-07-13 19:51       ` Thomas Monjalon
2022-07-15 15:33         ` Thomas Monjalon
2022-07-14  9:20       ` Bruce Richardson
2022-07-14 10:07         ` Thomas Monjalon
2022-07-14 14:50         ` Ferruh Yigit
2022-07-14 15:03           ` Ferruh Yigit
2022-07-15 15:32             ` Thomas Monjalon
2022-07-14  9:30       ` David Marchand
2021-12-01 16:31   ` [PATCH v3 1/2] doc: note KNI alternatives Morten Brørup
2022-11-24 10:31     ` Ferruh Yigit
2022-11-24 11:40   ` [PATCH v5] " Ferruh Yigit
2022-11-24 16:55     ` Stephen Hemminger
2022-11-24 17:08       ` Ferruh Yigit
2022-11-24 17:15     ` [PATCH v6] " Ferruh Yigit
2022-11-26 21:11       ` Thomas Monjalon

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