[PATCH v2 00/10] net/mlx5: per-queue Tx rate limiting via packet pacing

Vincent Jardin
2026-03-10T23:27:35Z

This series adds per-queue Tx data-rate limiting to the mlx5 PMD using
hardware packet pacing (PP), and a symmetric rte_eth_get_queue_rate_limit()
ethdev API to read back the configured rate.

Each Tx queue can be assigned an individual rate (in Mbps) at runtime via
rte_eth_set_queue_rate_limit(). The mlx5 implementation allocates a
dedicated PP index per rate from the HW rate table, programs it into the
SQ via modify_sq, and shares identical rates across queues to conserve
table entries. A PMD-specific API exposes per-queue PP diagnostics and
rate table capacity.

Patch breakdown:

1. doc/nics/mlx5: fix stale packet pacing documentation
2-3. common/mlx5: query PP capabilities and extend SQ modify
4-6. net/mlx5: per-queue PP infrastructure, rate_limit callback,
burst pacing devargs (tx_burst_bound, tx_typical_pkt_sz)
7. net/mlx5: testpmd command to query per-queue rate state
8. ethdev: add rte_eth_get_queue_rate_limit() symmetric getter
9. net/mlx5: share PP rate table entries across queues
10. net/mlx5: rate table capacity query API

Usage with testpmd:
set port 0 queue 0 rate 1000
set port 0 queue 1 rate 5000
set port 0 queue 0 rate 0 # disable
mlx5 port 0 txq 0 rate show # query

Changes since v1:

Addressed review feedback from Stephen Hemminger's AI:

Patch 4 (per-queue packet pacing infrastructure):
- Validate rate_mbps against HCA packet_pacing_min_rate and
packet_pacing_max_rate bounds; return -ERANGE on out-of-range
- Widen rate_kbps from uint32_t to uint64_t to prevent
overflow on rate_mbps * 1000
- Remove early mlx5_txq_free_pp_rate_limit() call from the
allocator (moved to caller, see patch 5)

Patch 5 (support per-queue rate limiting):
- Fix PP index leak on modify_sq failure: allocate new PP into a
temporary struct mlx5_txq_rate_limit; only swap into txq_ctrl->rl
after modify_sq succeeds. On failure the old PP context stays intact.
- Set rte_errno = -ret before returning errors from both the
disable (tx_rate=0) and enable paths

Patch 7 (testpmd command to query per-queue rate limit):
- Fix inverted rte_eth_tx_queue_is_valid() return value check:
was "if (rte_eth_tx_queue_is_valid(...))" (accepts invalid queues),
changed to "if (rte_eth_tx_queue_is_valid(...) != 0)"

Patch 8 (ethdev getter):
- Add release note for rte_eth_get_queue_rate_limit() in
doc/guides/rel_notes/release_26_03.rst

Patch 10 (rate table capacity query):
- Replace uint16_t seen[RTE_MAX_QUEUES_PER_PORT] (2 KB stack array)
with heap-allocated mlx5_malloc(priv->txqs_n, ...) + mlx5_free()
- Add early return when txqs == NULL || txqs_n == 0
- Document in the API Doxygen that "used" reflects only the queried
port's queues; other ports on the same device may also consume
rate table entries
- Add -ENOMEM to documented return values
- Add release note for mlx5 per-queue rate limiting

Not addressed in v2 (requires discussion):

- Patch 8: ethdev API breadth: rte_eth_get_queue_rate_limit()
is currently only implemented by mlx5. Other PMDs (ixgbe, i40e, ice)
would need implementations for full consistency. Feedbacks are
welcomed.

Testing:
- Build: GCC, no warnings
- devtools/check-git-log.sh -n 11: 11/11 valid
- devtools/checkpatches.sh -n 11: 10/11 valid (pre-existing
stdout warning in testpmd command, not introduced by this series)
- devtools/check-doc-vs-code.sh: clean
- devtools/check-meson.py: clean

Hardware tested:
- ConnectX-6 Dx (packet pacing with MLX5_DATA_RATE)

Vincent Jardin (10):
doc/nics/mlx5: fix stale packet pacing documentation
common/mlx5: query packet pacing rate table capabilities
common/mlx5: extend SQ modify to support rate limit update
net/mlx5: add per-queue packet pacing infrastructure
net/mlx5: support per-queue rate limiting
net/mlx5: add burst pacing devargs
net/mlx5: add testpmd command to query per-queue rate limit
ethdev: add getter for per-queue Tx rate limit
net/mlx5: share pacing rate table entries across queues
net/mlx5: add rate table capacity query API

doc/guides/nics/mlx5.rst | 125 +++++++++++++++-----
doc/guides/rel_notes/release_26_03.rst | 10 ++
drivers/common/mlx5/mlx5_devx_cmds.c | 20 ++++
drivers/common/mlx5/mlx5_devx_cmds.h | 14 ++-
drivers/net/mlx5/mlx5.c | 46 ++++++++
drivers/net/mlx5/mlx5.h | 13 +++
drivers/net/mlx5/mlx5_testpmd.c | 93 +++++++++++++++
drivers/net/mlx5/mlx5_tx.c | 105 ++++++++++++++++-
drivers/net/mlx5/mlx5_tx.h | 5 +
drivers/net/mlx5/mlx5_txpp.c | 86 ++++++++++++++
drivers/net/mlx5/mlx5_txq.c | 151 +++++++++++++++++++++++++
drivers/net/mlx5/rte_pmd_mlx5.h | 62 ++++++++++
lib/ethdev/ethdev_driver.h | 7 ++
lib/ethdev/rte_ethdev.c | 28 +++++
lib/ethdev/rte_ethdev.h | 24 ++++
15 files changed, 755 insertions(+), 33 deletions(-)

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2.43.0