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From: David Marchand <david.marchand@redhat.com>
To: Ferruh Yigit <ferruh.yigit@intel.com>
Cc: dev <dev@dpdk.org>, Keith Wiles <keith.wiles@intel.com>,
	 Stephen Hemminger <stephen@networkplumber.org>,
	Thomas Monjalon <thomas@monjalon.net>,
	 "Mcnamara, John" <john.mcnamara@intel.com>
Subject: Re: [dpdk-dev] [PATCH] doc: note KNI alternatives and deprecation plan
Date: Fri, 20 Aug 2021 14:58:33 +0200
Message-ID: <CAJFAV8xBuz8NB-NgRmGHE5845-2bAkifcmYfcqfLHccgiyVcow@mail.gmail.com> (raw)
In-Reply-To: <20210623173142.3803801-1-ferruh.yigit@intel.com>

On Wed, Jun 23, 2021 at 7:32 PM 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.

Some suggestions on wording below, feel free to ignore if this sounds
like French ;-).


>
> 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/>`_
The* KNI kernel module will be moved* (Olivier comment) to ...

> +   repository by the `DPDK technical board decision <https://mails.dpdk.org/archives/dev/2021-January/197077.html>`_.
repository following* the `...`_.

I'd move this first part in doc/guides/rel_notes/deprecation.rst
and/or release notes.
Then, reword this as:

> +   Also there is a `long term plan <https://mails.dpdk.org/archives/dev/2021-May/209026.html>`_ to deprecate the KNI.

The `long term plan...`_ is* to deprecate KNI, see <XXX link to
deprecation notice/release notes>.


> +
> +   :ref:`virtio_user_as_exceptional_path` alternative is preferred way for

is one/a* preferred way

> +   interfacing with Linux network stack as it is being in-kernel solution and

interfacing with the* Linux network stack as it is a* in-kernel and

> +   similar performance expectations.

has* 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

KNI provides* an interface ...

> +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

The* main use case of KNI is to* ...

> +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`
> +

+1 to Olivier comment, for making virtio-user first.


> +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:

Not sure why we need an extra DPDK, KNI alone is enough.


> +
> +* 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

OSV as in OS vendors, right? ok for me.


> +  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.

of net devices control commands*

>
>  The components of an application using the DPDK Kernel NIC Interface are shown in :numref:`figure_kernel_nic_intf`.
>
> --
> 2.31.1
>


-- 
David Marchand


  parent reply	other threads:[~2021-08-20 12:58 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-23 17:31 Ferruh Yigit
2021-06-23 18:33 ` Stephen Hemminger
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 [this message]
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
2021-12-01 16:31   ` [PATCH v3 1/2] doc: note KNI alternatives Morten Brørup

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