Re: [PATCH net 1/1] net/mlx5e: Set EQE based as default TX interrupt moderation mode

[David Miller <davem@davemloft.net>]

From: Saeed Mahameed <saeedm@mellanox.com>
Date: Fri, 30 Mar 2018 15:50:08 -0700

> From: Tal Gilboa <talgi@mellanox.com>
> 
> The default TX moderation mode was mistakenly set to CQE based. The
> intention was to add a control ability in order to improve some specific
> use-cases. In general, we prefer to use EQE based moderation as it gives
> much better numbers for the common cases.
> 
> CQE based causes a degradation in the common case since it resets the
> moderation timer on CQE generation. This causes an issue when TSO is
> well utilized (large TSO sessions). The timer is set to 16us so traffic
> of ~64KB TSO sessions per second would mean timer reset (CQE per TSO
> session -> long time between CQEs). In this case we quickly reach the
> tcp_limit_output_bytes (256KB by default) and cause a halt in TX traffic.
> 
> By setting EQE based moderation we make sure timer would expire after
> 16us regardless of the packet rate.
> This fixes an up to 40% packet rate and up to 23% bandwidth degradtions.
> 
> Fixes: 0088cbbc4b66 ("net/mlx5e: Enable CQE based moderation on TX CQ")
> Signed-off-by: Tal Gilboa <talgi@mellanox.com>
> Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

Applied and queued up for -stable.