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From: Morten Brørup <mb@smartsharesystems.com>
To: "Ferruh Yigit" <ferruh.yigit@intel.com>
Cc: <dev@dpdk.org>,
	"Olivier Matz Olivier Matz" <olivier.matz@6wind.com>,
	"David Marchand David Marchand" <david.marchand@redhat.com>,
	"Stephen Hemminger Stephen Hemminger"
	<stephen@networkplumber.org>, "Elad Nachman" <eladv6@gmail.com>,
	"Igor Ryzhov" <iryzhov@nfware.com>, "Dan Gora" <dg@adax.com>
Subject: RE: [PATCH v3 1/2] doc: note KNI alternatives
Date: Wed, 1 Dec 2021 17:31:14 +0100
Message-ID: <98CBD80474FA8B44BF855DF32C47DC35D86D2D@smartserver.smartshare.dk> (raw)
In-Reply-To: <20211124171609.3101896-1-ferruh.yigit@intel.com>

> From: Ferruh Yigit [mailto:ferruh.yigit@intel.com]
> Sent: Wednesday, 24 November 2021 18.16
> 
> Add more information on alternatives of KNI and the cons of KNI against
> these alternatives.
> 
> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
> ---
> Cc: Olivier Matz Olivier Matz <olivier.matz@6wind.com>
> Cc: David Marchand David Marchand <david.marchand@redhat.com>
> Cc: Stephen Hemminger Stephen Hemminger <stephen@networkplumber.org>
> Cc: Elad Nachman <eladv6@gmail.com>
> Cc: Igor Ryzhov <iryzhov@nfware.com>
> Cc: Dan Gora <dg@adax.com>
> 
> v3:
> * reference tap document directly instead of adding label to it.
> ---
>  .../prog_guide/kernel_nic_interface.rst       | 34 +++++++++++++++++--
>  1 file changed, 31 insertions(+), 3 deletions(-)
> 
> diff --git a/doc/guides/prog_guide/kernel_nic_interface.rst
> b/doc/guides/prog_guide/kernel_nic_interface.rst
> index 1ce03ec1a374..f5a8b7c0782c 100644
> --- a/doc/guides/prog_guide/kernel_nic_interface.rst
> +++ b/doc/guides/prog_guide/kernel_nic_interface.rst
> @@ -6,16 +6,44 @@
>  Kernel NIC Interface
>  ====================
> 
> +.. Note::
> +
> +   :ref:`virtio_user_as_exceptional_path` alternative is the preferred
> way for
> +   interfacing with the Linux network stack as it is an in-kernel
> solution and
> +   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 provides an interface with the kernel network stack and allows
> management of
> +DPDK ports using standard Linux net tools such as ``ethtool``,
> ``ifconfig`` and
> +``tcpdump``.
> +
> +The main use case of KNI is to 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:`virtio_user_as_exceptional_path`
> +
> +#. :doc:`../nics/tap` as wrapper to `Linux tun/tap
> +   <https://www.kernel.org/doc/Documentation/networking/tuntap.txt>`_
> +
> +The benefits of using the 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 KNI are:

Consider if "disadvantages" is more appropriate than "cons". (I'm not a native English speaker.)

> +
> +* It is out-of-tree Linux kernel module and it can't be distributed as
> binary as
> +  part of operating system vendor 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 net devices control commands are supported by KNI.

If it is still relevant, add something along the lines of:
* Requires dedicated kernel cores.

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

Could you perhaps also promote the virtio-user documentation by moving it from the HowTo Guides to the Programmer's Guide?

-Morten


      parent reply	other threads:[~2021-12-01 16:31 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-23 17:31 [dpdk-dev] [PATCH] doc: note KNI alternatives and deprecation plan 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
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   ` Morten Brørup [this message]

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