netdev - [PATCH v8 net-next 0/7] Add tx push buf len param to ethtool

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Message-ID: <20230323195923.1731790-1-shayagr@amazon.com>
Date:   Thu, 23 Mar 2023 21:59:16 +0200
From:   Shay Agroskin <shayagr@...zon.com>
To:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, <netdev@...r.kernel.org>
CC:     Shay Agroskin <shayagr@...zon.com>,
        "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>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Andrew Lunn <andrew@...n.ch>,
        Johannes Berg <johannes@...solutions.net>,
        Edward Cree <ecree.xilinx@...il.com>,
        Florian Westphal <fw@...len.de>
Subject: [PATCH v8 net-next 0/7] Add tx push buf len param to ethtool

Changes since v7:
- Changed netlink policy macro to a more elegant solution.

Changes since v6:
- Modify netlink policy macro to avoid evaluating the macro
  argument more than once.

Changes since v5:
- Added a print of the maximum tx-push-buf-len when user tries to
  configure a value which exceeds it.

Changes 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 (6):
  netlink: Add a macro to set policy message with format string
  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/linux/netlink.h                       |  13 +
 include/uapi/linux/ethtool_netlink.h          |   2 +
 net/ethtool/netlink.h                         |   2 +-
 net/ethtool/rings.c                           |  34 ++-
 11 files changed, 340 insertions(+), 124 deletions(-)

-- 
2.25.1