netdev - Re: [PATCH v2 net-next] net/mlx5e: Report rx_discards_phy via rx_fifo

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Message-ID: <CALOAHbCQeoPfQnXK-Zt6+Fc-UuNAn12UwgT_y11gzrmtnWWpUQ@mail.gmail.com>
Date: Fri, 15 Nov 2024 11:56:38 +0800
From: Yafang Shao <laoar.shao@...il.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: ttoukan.linux@...il.com, gal@...dia.com, saeedm@...dia.com, 
	tariqt@...dia.com, leon@...nel.org, netdev@...r.kernel.org, 
	linux-rdma@...r.kernel.org
Subject: Re: [PATCH v2 net-next] net/mlx5e: Report rx_discards_phy via rx_fifo_errors

On Fri, Nov 15, 2024 at 10:27 AM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Thu, 14 Nov 2024 10:17:11 +0800 Yafang Shao wrote:
> > - *   Not recommended for use in drivers for high speed interfaces.
>
> I thought I suggested we provide clear guidance on this counter being
> related to processing pipeline being to slow, vs host backpressure.
> Just deleting the line that says "don't use" is not going to cut it :|

Hello Jakub,

After investigating other network drivers, I found that they all
report this metric to rx_missed_errors:

- i40e
  The corresponding ethtool metric is port.rx_discards, which was
mapped to rx_missed_errors in commit 5337d2949733 ("i40e: Add
rx_missed_errors for buffer exhaustion").

- broadcom
  The equivalent metric is rx_total_discard_pkts, reported as
rx_missed_errors in commit c0c050c58d84 ("bnxt_en: New Broadcom
ethernet driver")

Given this, it seems we should align with the standard practice and
report this metric to rx_missed_errors.

Tariq, what are your thoughts?

--
Regards

Yafang