[v3,1/2] doc: note KNI alternatives
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Commit Message
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(-)
Comments
> 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
On 12/1/2021 4:31 PM, Morten Brørup wrote:
>> 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.)
>
Both fine for me, OK to use 'disadvantages'.
>> +
>> +* 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.
>
ack
>>
>> 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?
>
Hi Morten,
This is an old patch, I assumed merged v4 by Thomas superseded this
patch, but it seems this patch was not involved in that, so I will make
a new version.
For the virtio-user documentation, no objection to move it to
programmer's guide, I hope Maxime and Chenbo can help there.
@@ -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:
+
+* 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`.