netdev - Re: [PATCH V1 net-next 5/5] net: ena: Add devlink documentation

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Date:   Mon, 9 Jan 2023 15:00:15 +0900
From:   Kuniyuki Iwashima <kuniyu@...zon.com>
To:     <darinzon@...zon.com>
CC:     <akiyano@...zon.com>, <alisaidi@...zon.com>, <davem@...emloft.net>,
        <itzko@...zon.com>, <kuba@...nel.org>, <matua@...zon.com>,
        <nafea@...zon.com>, <ndagan@...zon.com>, <netdev@...r.kernel.org>,
        <osamaabb@...zon.com>, <saeedb@...zon.com>, <shayagr@...zon.com>,
        <zorik@...zon.com>, <kuniyu@...zon.com>
Subject: Re: [PATCH V1 net-next 5/5] net: ena: Add devlink documentation

From:   David Arinzon <darinzon@...zon.com>
Date:   Sun, 8 Jan 2023 10:35:33 +0000
> Update the documentation with a devlink section, the
> added files, as well as large LLQ enablement.
> 
> Signed-off-by: Shay Agroskin <shayagr@...zon.com>
> Signed-off-by: David Arinzon <darinzon@...zon.com>
> ---
>  .../device_drivers/ethernet/amazon/ena.rst    | 30 +++++++++++++++++++

Each driver's devlink doc exists under Documentation/networking/devlink/ and
linked from index.html there.

We should duplicate this doc under Documentation/networking/devlink/ or link from
the index.html ?


>  1 file changed, 30 insertions(+)
> 
> diff --git a/Documentation/networking/device_drivers/ethernet/amazon/ena.rst b/Documentation/networking/device_drivers/ethernet/amazon/ena.rst
> index 8bcb173e0353..1229732a8c91 100644
> --- a/Documentation/networking/device_drivers/ethernet/amazon/ena.rst
> +++ b/Documentation/networking/device_drivers/ethernet/amazon/ena.rst
> @@ -53,6 +53,7 @@ ena_common_defs.h   Common definitions for ena_com layer.
>  ena_regs_defs.h     Definition of ENA PCI memory-mapped (MMIO) registers.
>  ena_netdev.[ch]     Main Linux kernel driver.
>  ena_ethtool.c       ethtool callbacks.
> +ena_devlink.[ch]    devlink files (see `devlink support`_ for more info)
>  ena_pci_id_tbl.h    Supported device IDs.
>  =================   ======================================================
>  
> @@ -253,6 +254,35 @@ RSS
>  - The user can provide a hash key, hash function, and configure the
>    indirection table through `ethtool(8)`.
>  
> +.. _`devlink support`:
> +DEVLINK SUPPORT
> +===============
> +.. _`devlink`: https://www.kernel.org/doc/html/latest/networking/devlink/index.html
> +
> +`devlink`_ supports toggling LLQ entry size between the default 128 bytes and 256
> +bytes.
> +A 128 bytes entry size allows for a maximum of 96 bytes of packet header size
> +which sometimes is not enough (e.g. when using tunneling).
> +Increasing LLQ entry size to 256 bytes, allows a maximum header size of 224
> +bytes. This comes with the penalty of reducing the number of LLQ entries in the
> +TX queue by 2 (i.e. from 1024 to 512).
> +
> +The entry size can be toggled by enabling/disabling the large_llq_header devlink
> +param and reloading the driver to make it take effect, e.g.
> +
> +.. code-block:: shell
> +
> +  sudo devlink dev param set pci/0000:00:06.0 name large_llq_header value true cmode driverinit
> +  sudo devlink dev reload pci/0000:00:06.0
> +
> +One way to verify that the TX queue entry size has indeed increased is to check
> +that the maximum TX queue depth is 512. This can be checked, for example, by
> +using:
> +
> +.. code-block:: shell
> +
> +  ethtool -g [interface]
> +
>  DATA PATH
>  =========
>  
> -- 
> 2.38.1