netdev - Re: [PATCH v5 net-next 0/6] Add tx push buf len param to ethtool

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Message-ID: <ZBN1HeMxbaXvpH+Z@localhost.localdomain>
Date:   Thu, 16 Mar 2023 20:59:25 +0100
From:   Michal Kubiak <michal.kubiak@...el.com>
To:     Shay Agroskin <shayagr@...zon.com>
CC:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, <netdev@...r.kernel.org>,
        "Woodhouse, David" <dwmw@...zon.com>,
        "Machulsky, Zorik" <zorik@...zon.com>,
        "Matushevsky, Alexander" <matua@...zon.com>,
        Saeed Bshara <saeedb@...zon.com>,
        "Wilson, Matt" <msw@...zon.com>,
        "Liguori, Anthony" <aliguori@...zon.com>,
        "Bshara, Nafea" <nafea@...zon.com>,
        "Belgazal, Netanel" <netanel@...zon.com>,
        "Saidi, Ali" <alisaidi@...zon.com>,
        "Herrenschmidt, Benjamin" <benh@...zon.com>,
        "Kiyanovski, Arthur" <akiyano@...zon.com>,
        "Dagan, Noam" <ndagan@...zon.com>,
        "Arinzon, David" <darinzon@...zon.com>,
        "Itzko, Shahar" <itzko@...zon.com>,
        "Abboud, Osama" <osamaabb@...zon.com>
Subject: Re: [PATCH v5 net-next 0/6] Add tx push buf len param to ethtool

On Thu, Mar 16, 2023 at 04:27:00PM +0200, Shay Agroskin wrote:
> Changed since v4:
> - Added advertisement for tx-push-mode in ENA driver
> - Modified the documentation to make the distinction from
>   tx-copybreak clearer
> 
> Changes since v3:
> - Removed RFC tag and added a Jakub's signoff on one of the first patch
> 
> Changes since v2:
> - Added a check that the driver advertises support for TX push buffer
>   instead of defaulting the response to 0.
> - Moved cosmetic changes to their own commits
> - Removed usage of gotos which goes against Linux coding style
> - Make ENA driver reject an attempt to configure TX push buffer when
>   it's not supported (no LLQ is used)
> 
> Changes since v1:
> - Added the new ethtool param to generic netlink specs
> - Dropped dynamic advertisement of tx push buff support in ENA.
>   The driver will advertise it for all platforms
> 
> This patchset adds a new sub-configuration to ethtool get/set queue
> params (ethtool -g) called 'tx-push-buf-len'.
> 
> This configuration specifies the maximum number of bytes of a
> transmitted packet a driver can push directly to the underlying
> device ('push' mode). The motivation for pushing some of the bytes to
> the device has the advantages of
> 
> - Allowing a smart device to take fast actions based on the packet's
>   header
> - Reducing latency for small packets that can be copied completely into
>   the device
> 
> This new param is practically similar to tx-copybreak value that can be
> set using ethtool's tunable but conceptually serves a different purpose.
> While tx-copybreak is used to reduce the overhead of DMA mapping and
> makes no sense to use if less than the whole segment gets copied,
> tx-push-buf-len allows to improve performance by analyzing the packet's
> data (usually headers) before performing the DMA operation.
> 
> The configuration can be queried and set using the commands:
> 
>     $ ethtool -g [interface]
> 
>     # ethtool -G [interface] tx-push-buf-len [number of bytes]
> 
> This patchset also adds support for the new configuration in ENA driver
> for which this parameter ensures efficient resources management on the
> device side.
> 
> David Arinzon (1):
>   net: ena: Add an option to configure large LLQ headers
> 
> Shay Agroskin (5):
>   ethtool: Add support for configuring tx_push_buf_len
>   net: ena: Make few cosmetic preparations to support large LLQ
>   net: ena: Recalculate TX state variables every device reset
>   net: ena: Add support to changing tx_push_buf_len
>   net: ena: Advertise TX push support
> 
>  Documentation/netlink/specs/ethtool.yaml      |   8 +
>  Documentation/networking/ethtool-netlink.rst  |  47 ++--
>  drivers/net/ethernet/amazon/ena/ena_eth_com.h |   4 +
>  drivers/net/ethernet/amazon/ena/ena_ethtool.c |  66 ++++-
>  drivers/net/ethernet/amazon/ena/ena_netdev.c  | 259 +++++++++++-------
>  drivers/net/ethernet/amazon/ena/ena_netdev.h  |  15 +-
>  include/linux/ethtool.h                       |  14 +-
>  include/uapi/linux/ethtool_netlink.h          |   2 +
>  net/ethtool/netlink.h                         |   2 +-
>  net/ethtool/rings.c                           |  33 ++-
>  10 files changed, 326 insertions(+), 124 deletions(-)
> 

The series looks very good to me.

Thanks,
Michal

For the series.
Reviewed-by: Michal Kubiak <michal.kubiak@...el.com>

> -- 
> 2.25.1
>