On Wed, Aug 1, 2018 at 2:52 PM, Saeed Mahameed [off-list ref] wrote:

From: Eran Ben Elisha <redacted>

Add support for two driver parameters via devlink params interface:
- Congestion action
        HW mechanism in the PCIe buffer which monitors the amount of
        consumed PCIe buffer per host. This mechanism supports the
        following actions in case of threshold overflow:
        - disabled - NOP (Default)
        - drop
        - mark - Mark CE bit in the CQE of received packet

Any chance you could clarify the differences between "disabled" and
"drop"? I am assuming the "drop" is a head-of-line drop versus the
"disabled" being a incoming packet drop?

Also I still don't see this as necessarily being all that unique of a
feature/issue. Basically being PCIe bus limited is not all that
uncommon of a thing and has existed since the early days of PCI. In
the case of the Intel NICs we just throw a warning and end up dropping
the incoming packets instead of providing the two other options you
have listed.

- Congestion mode
        - aggressive - Aggressive static trigger threshold (Default)
        - dynamic - Dynamically change the trigger threshold

These driver-specific params enable the NIC HW workaround to handle
buffer congestion on the current NIC generation.

Is there any documentation anywhere for any of these features? In the
patch set I see you adding interfaces, but I don't see them documented
anywhere.

Signed-off-by: Eran Ben Elisha <redacted>
Reviewed-by: Moshe Shemesh <redacted>
Reviewed-by: Jiri Pirko <redacted>
Signed-off-by: Saeed Mahameed <redacted>
---
 .../net/ethernet/mellanox/mlx5/core/devlink.c | 204 +++++++++++++++++-
 1 file changed, 203 insertions(+), 1 deletion(-)

Ideally there should be some documentation going into the kernel when
you extend the devlink interface at least so that I know how to use
your new interfaces when you define them. Just updating devlink.c
seems like a messy way to do things.

- Alex