linux-kernel - Re: [RFC net-next v3 0/2] mlx5: Add netdev-genl queue stats

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Message-ID: <ZlkgVJbRpkzx6rTI@LQ3V64L9R2>
Date: Thu, 30 May 2024 17:56:52 -0700
From: Joe Damato <jdamato@...tly.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Saeed Mahameed <saeedm@...dia.com>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, 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>,
	Richard Cochran <richardcochran@...il.com>,
	Tariq Toukan <tariqt@...dia.com>
Subject: Re: [RFC net-next v3 0/2] mlx5: Add netdev-genl queue stats

On Thu, May 30, 2024 at 05:39:02PM -0700, Jakub Kicinski wrote:
> On Thu, 30 May 2024 17:15:25 -0700 Joe Damato wrote:
> > > Why to base, and not report them as queue stats?
> > > 
> > > Judging by mlx5e_update_tx_netdev_queues() calls sprinkled in
> > > ../mlx5/core/en/htb.c it seems that the driver will update the
> > > real_num_tx_queues accordingly. And from mlx5e_qid_from_qos()
> > > it seems like the inverse calculation is:
> > > 
> > > i - (chs->params.num_channels + is_ptp)*mlx5e_get_dcb_num_tc(&chs->params)
> > > 
> > > But really, isn't it enough to use priv->txq2sq[i] for the active
> > > queues, and not active ones you've already covered?  
> > 
> > This is what I proposed in the thread for the v2, but Tariq
> > suggested a different approach he liked more, please see this
> > message for more details:
> > 
> >   https://lore.kernel.org/netdev/68225941-f3c3-4335-8f3d-edee43f59033@gmail.com/
> > 
> > I attempted to implement option 1 as he described in his message.
> 
> I see, although it sounds like option 2 would also work.

I don't really mind either way; from Tariq's message it sounded like
he preferred option 1, so I tried to implement that thinking that it would be
my best bet at getting this done.

If option 2 is easier/preferred for some reason... it seems like
(other than the locking I forgot to include) the base implementation
in v2 was correct and I could use what I proposed in the thread for
the tx stats, which was:

  mutex_lock(&priv->state_lock);
  if (priv->channels.num > 0) {
          sq = priv->txq2sq[i];
          stats->packets = sq->stats->packets;
          stats->bytes = sq->stats->bytes;
  }
  mutex_unlock(&priv->state_lock);

And I would have implemented option 2... IIUC.