[PATCH net-next v3 00/12] net/mlx5e: Add support for devmem and io_uring TCP zero-copy

Mark Bloch
2025-06-09T14:59:00Z

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Quick note before diving into the series details, Tariq is on vacation
for a few days, I’ll be handling the mlx5 core/netdev submissions
in his absence.

This series adds support for zerocopy rx TCP with devmem and io_uring
for ConnectX7 NICs and above. For performance reasons and simplicity
HW-GRO will also be turned on when header-data split mode is on.

Performance
===========

Test setup:

* CPU: Intel(R) Xeon(R) Platinum 8380 CPU @ 2.30GHz (single NUMA)
* NIC: ConnectX7
* Benchmarking tool: kperf [0]
* Single TCP flow
* Test duration: 60s

With application thread and interrupts pinned to the *same* core:

|------+-----------+----------|
| MTU | epoll | io_uring |
|------+-----------+----------|
| 1500 | 61.6 Gbps | 114 Gbps |
| 4096 | 69.3 Gbps | 151 Gbps |
| 9000 | 67.8 Gbps | 187 Gbps |
|------+-----------+----------|

The CPU usage for io_uring is 95%.

Reproduction steps for io_uring:

server --no-daemon -a 2001:db8::1 --no-memcmp --iou --iou_sendzc \
--iou_zcrx --iou_dev_name eth2 --iou_zcrx_queue_id 2

server --no-daemon -a 2001:db8::2 --no-memcmp --iou --iou_sendzc

client --src 2001:db8::2 --dst 2001:db8::1 \
--msg-zerocopy -t 60 --cpu-min=2 --cpu-max=2

Patch overview:
================

First, a netmem API for skb_can_coalesce is added to the core to be able
to do skb fragment coalescing on netmems.

The next patches introduce some cleanups in the internal SHAMPO code and
improvements to hw gro capability checks in FW.

A separate page_pool is introduced for headers, to be used only when
the rxq has a memory provider. Ethtool stats are added as well.

Then the driver is converted to use the netmem API and to allow support
for unreadable netmem page pool.

The queue management ops are implemented.

Finally, the tcp-data-split ring parameter is exposed.

Changelog
=========

Changes from v2 [2]:
- Added support for netmem TX.
- Changed skb_can_coalesce_netmem() based on Mina's suggestion.
- Reworked tcp_data_split setting to no longer change HW-GRO in
wanted_features.
- Switched to a single page pool when rxq has no memory providers.

Changes from v1 [1]:
- Added support for skb_can_coalesce_netmem().
- Avoid netmem_to_page() casts in the driver.
- Fixed code to abide 80 char limit with some exceptions to avoid
code churn.

References
==========
[0] kperf: git://git.kernel.dk/kperf.git
[1] v1: https://lore.kernel.org/all/20250116215530.158886-1-saeed@kernel.org/
[2] v2: https://lore.kernel.org/all/1747950086-1246773-1-git-send-email-tariqt@nvidia.com/

Dragos Tatulea (3):
net: Allow const args for of page_to_netmem()
net: Add skb_can_coalesce for netmem
net/mlx5e: Add TX support for netmems

Saeed Mahameed (9):
net/mlx5e: SHAMPO: Reorganize mlx5_rq_shampo_alloc
net/mlx5e: SHAMPO: Remove redundant params
net/mlx5e: SHAMPO: Improve hw gro capability checking
net/mlx5e: SHAMPO: Separate pool for headers
net/mlx5e: SHAMPO: Headers page pool stats
net/mlx5e: Convert over to netmem
net/mlx5e: Add support for UNREADABLE netmem page pools
net/mlx5e: Implement queue mgmt ops and single channel swap
net/mlx5e: Support ethtool tcp-data-split settings

drivers/net/ethernet/mellanox/mlx5/core/en.h | 11 +-
.../ethernet/mellanox/mlx5/core/en/params.c | 36 ++-
.../net/ethernet/mellanox/mlx5/core/en/txrx.h | 3 +-
.../ethernet/mellanox/mlx5/core/en_ethtool.c | 33 +-
.../net/ethernet/mellanox/mlx5/core/en_main.c | 305 +++++++++++++-----
.../net/ethernet/mellanox/mlx5/core/en_rx.c | 136 ++++----
.../ethernet/mellanox/mlx5/core/en_stats.c | 54 ++++
.../ethernet/mellanox/mlx5/core/en_stats.h | 24 ++
include/linux/skbuff.h | 12 +-
include/net/netmem.h | 2 +-
10 files changed, 449 insertions(+), 167 deletions(-)

base-commit: 2c7e4a2663a1ab5a740c59c31991579b6b865a26
--
2.34.1