[RFC,v3,net-next,0/5] Add tx push buf len param to ethtool

Message

Shay Agroskin March 7, 2023, 10:24 a.m. UTC

Changed 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)

Changed 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 (4):
  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

 Documentation/netlink/specs/ethtool.yaml      |   8 +
 Documentation/networking/ethtool-netlink.rst  |  43 +--
 drivers/net/ethernet/amazon/ena/ena_eth_com.h |   4 +
 drivers/net/ethernet/amazon/ena/ena_ethtool.c |  57 +++-
 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, 313 insertions(+), 124 deletions(-)

Comments

Jakub Kicinski March 9, 2023, 2:34 a.m. UTC | #1

On Tue, 7 Mar 2023 12:24:53 +0200 Shay Agroskin wrote:
> Changed 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)

LGTM!

Feel free to add my:

Signed-off-by: Jakub Kicinski <[e-mail]>

On patch one, because checkpatch will complain otherwise.

And repost as non-RFC.