[PATCH iwl-next v5 0/2] i40e: add runtime-tunable ATR sample rate

[mheib@redhat.com]

From: Mohammad Heib <mheib@redhat.com>

This series makes the Flow Director ATR sample rate configurable at
runtime through a devlink parameter.

On systems with many queues and high-rate TCP workloads, the fixed
default sampling interval can cause frequent Flow Director
reprogramming and TCP packet reordering. The optimal interval depends
on the workload and system configuration.

Patch 1 moves atr_sample_rate from per-ring to PF level, since it is
a global policy. It also triggers a PF reset when re-enabling ATR via
ethtool private flags so that fd_ena is reprogrammed in the TX queue
HW context.

Patch 2 exposes atr_sample_rate as a devlink runtime parameter so
administrators can tune it without rebuilding the driver.

Testing with iperf3 -t 60 showed ~7k TCP reordering events at the
default sample rate (20). Setting atr_sample_rate to 10000 reduced
reordering to ~769 (~90% reduction).

Changes since v4:
- Folded the PF reset patch into patch 1 for bisect cleanliness
  (was patch 3/3 in v4)
- Skip PF reset when FD_SB (ntuple) already holds fd_ena high,
  avoiding unnecessary traffic disruption
- Fix LLDP EEXIST path to not drop unrelated reset requests
  (reset_needed &= ~REBUILD_FLAG instead of = 0)
- Flush existing ATR entries when setting atr_sample_rate to 0 via
  devlink, so stale filters do not persist on devices without HW
  ATR eviction
- Documentation: clarify that the sampling interval is per Tx queue
  and counts TCP packets only; fix formatting

Mohammad Heib (2):
  i40e: move ATR sample rate from ring to PF level
  i40e: add devlink parameter for Flow Director ATR sample rate

 Documentation/networking/devlink/i40e.rst     | 21 +++++++++
 drivers/net/ethernet/intel/i40e/i40e.h        |  1 +
 .../net/ethernet/intel/i40e/i40e_devlink.c    | 46 +++++++++++++++++++
 .../net/ethernet/intel/i40e/i40e_ethtool.c    | 12 ++++-
 drivers/net/ethernet/intel/i40e/i40e_main.c   |  9 ++--
 drivers/net/ethernet/intel/i40e/i40e_txrx.c   |  6 ++-
 drivers/net/ethernet/intel/i40e/i40e_txrx.h   |  3 +-
 7 files changed, 87 insertions(+), 11 deletions(-)

-- 
2.56.0