netdev - Re: [RFC PATCH net-next 0/2] Configuring PFC stall prevention via ethtool

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Date:   Thu, 16 Nov 2017 09:44:06 +0100
From:   Michal Kubecek <mkubecek@...e.cz>
To:     Eran Ben Elisha <eranbe@...lanox.com>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        "John W. Linville" <linville@...driver.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Gal Pressman <galp@...lanox.com>,
        Ariel Almog <ariela@...lanox.com>,
        Inbar Karmy <inbark@...lanox.com>
Subject: Re: [RFC PATCH net-next 0/2] Configuring PFC stall prevention via
 ethtool

On Wed, Nov 15, 2017 at 09:00:09PM +0200, Eran Ben Elisha wrote:
> From: Inbar Karmy <inbark@...lanox.com>
> 
> This RFC adds support for configuring PFC stall prevention through ethtool.
> 
> In the event where the device unexpectedly becomes unresponsive for a long
> period of time, flow control mechanism may propagate pause frames which will
> cause congestion spreading to the entire network.
> 
> To prevent this scenario, the device may implement a protection mechanism for
> monitoring and resolving such state.  The following patches allow the user to
> control the stall prevention functionality.
> 
> PFC stall prevention configuration is done via ethtool -a (pause).
> Two modes are introduced:
> Default - current behavior per driver.
> Auto - protection mechanism controlled automatically by the driver.
> Due to lack of extension ability of ethtool_ops set_pauseparam, a new
> ethtool_ops get_pfc_prevention_mode is introduced.

I don't like adding another ethtool_ops callback tightly tied to the
structures passed via ioctl() but when I started to think what to
suggest as an alternative, I started to wonder if it is really necessary
to add a new ethtool command at all. Couldn't this be handled as
a tunable?

Michal Kubecek

> I based this patch set on net-next commit 50895b9de1d3("tcp: highest_sack fix
> ").
> 
> Inbar Karmy (2):
>   ethtool: Add support for configuring PFC stall prevention in ethtool
>   net/mlx5e: PFC stall prevention support
> 
>  .../net/ethernet/mellanox/mlx5/core/en_ethtool.c   | 51 ++++++++++++++++++++
>  drivers/net/ethernet/mellanox/mlx5/core/port.c     | 56 ++++++++++++++++++----
>  include/linux/ethtool.h                            |  8 ++++
>  include/linux/mlx5/mlx5_ifc.h                      | 22 +++++++--
>  include/linux/mlx5/port.h                          |  5 ++
>  include/uapi/linux/ethtool.h                       | 20 ++++++++
>  net/core/ethtool.c                                 | 39 +++++++++++++++
>  7 files changed, 188 insertions(+), 13 deletions(-)
> 
> -- 
> 1.8.3.1
>