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From: Ferruh Yigit <ferruh.yigit@intel.com>
Cc: Ferruh Yigit <ferruh.yigit@intel.com>,
	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: [PATCH v3 1/2] doc: note KNI alternatives
Date: Wed, 24 Nov 2021 17:16:08 +0000
Message-ID: <20211124171609.3101896-1-ferruh.yigit@intel.com> (raw)
In-Reply-To: <20210623173142.3803801-1-ferruh.yigit@intel.com>

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>

* 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
+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:
+* 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.
 The components of an application using the DPDK Kernel NIC Interface are shown in :numref:`figure_kernel_nic_intf`.

  parent reply	other threads:[~2021-11-24 17:21 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 ` Ferruh Yigit [this message]
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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