linux-kernel - Re: [PATCH net-next 0/1] mlx5: Add netdev-genl queue stats

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Date: Wed, 8 May 2024 17:56:38 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Joe Damato <jdamato@...tly.com>
Cc: Tariq Toukan <ttoukan.linux@...il.com>, Zhu Yanjun
 <zyjzyj2000@...il.com>, linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org, saeedm@...dia.com, gal@...dia.com,
 nalramli@...tly.com, "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Leon Romanovsky <leon@...nel.org>, "open
 list:MELLANOX MLX5 core VPI driver" <linux-rdma@...r.kernel.org>, Paolo
 Abeni <pabeni@...hat.com>, Tariq Toukan <tariqt@...dia.com>
Subject: Re: [PATCH net-next 0/1] mlx5: Add netdev-genl queue stats

On Wed, 8 May 2024 16:24:08 -0700 Joe Damato wrote:
> > A possible reason for this difference is the queues included in the sum.
> > Our stats are persistent across configuration changes, so they doesn't reset
> > when number of channels changes for example.
> > 
> > We keep stats entries for al ring indices that ever existed. Our driver
> > loops and sums up the stats for all of them, while the stack loops only up
> > to the current netdev->real_num_rx_queues.
> > 
> > Can this explain the diff here?  
> 
> Yes, that was it. Sorry I didn't realize this case. My lab machine runs a
> script to adjust the queue count shortly after booting.
> 
> I disabled that and re-ran:
> 
>   NETIF=eth0 tools/testing/selftests/drivers/net/stats.py
> 
> and all tests pass.

Stating the obvious, perhaps, but in this case we should add the stats
from inactive queues to the base (which when the NIC is down means all
queues).