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

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Message-ID: <ZjxM9i1yFDRQ2f/s@ubuntu>
Date: Thu, 9 May 2024 04:11:34 +0000
From: Joe Damato <jdamato@...tly.com>
To: Jakub Kicinski <kuba@...nel.org>
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, May 08, 2024 at 07:08:39PM -0700, Jakub Kicinski wrote:
> On Thu, 9 May 2024 01:57:52 +0000 Joe Damato wrote:
> > If I'm following that right and understanding mlx5 (two things I am
> > unlikely to do simultaneously), that sounds to me like:
> > 
> > - mlx5e_get_queue_stats_rx and mlx5e_get_queue_stats_tx check if i <
> >   priv->channels.params.num_channels (instead of priv->stats_nch),
> 
> Yes, tho, not sure whether the "if i < ...num_channels" is even
> necessary, as core already checks against real_num_rx_queues.

OK, I'll omit the i < ... check in the v2, then.

> >   and when
> >   summing mlx5e_sq_stats in the latter function, it's up to
> >   priv->channels.params.mqprio.num_tc instead of priv->max_opened_tc.
> > 
> > - mlx5e_get_base_stats accumulates and outputs stats for everything from
> >   priv->channels.params.num_channels to priv->stats_nch, and
> 
> I'm not sure num_channels gets set to 0 when device is down so possibly
> from "0 if down else ...num_channels" to stats_nch.

Yea, it looks like priv->channels.params.num_channels is untouched on
ndo_stop, but:

mlx5e_close (ndo_close)
  mlx5e_close_locked
    mlx5e_close_channels
      priv->channels->num = 0;

and on open priv->channels->num is restored from 0 to
priv->channels.params.num_channels.

So, priv->channels->num to priv->stats_nch would be, I think, the inactive
queues. I'll give it a try locally real quick.

> >   priv->channels.params.mqprio.num_tc to priv->max_opened_tc... which
> >   should cover the inactive queues, I think.
> > 
> > Just writing that all out to avoid hacking up the wrong thing for the v2
> > and to reduce overall noise on the list :)