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

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Date: Fri, 3 May 2024 16:53:40 -0700
From: Joe Damato <jdamato@...tly.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Zhu Yanjun <zyjzyj2000@...il.com>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, tariqt@...dia.com, 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>
Subject: Re: [PATCH net-next 0/1] mlx5: Add netdev-genl queue stats

On Fri, May 03, 2024 at 02:58:08PM -0700, Jakub Kicinski wrote:
> On Fri, 3 May 2024 11:43:27 -0700 Joe Damato wrote:
> > 1. it includes the PTP stats that I don't include in my qstats, and/or
> > 2. some other reason I don't understand
> 
> Can you add the PTP stats to the "base" values? 
> I.e. inside mlx5e_get_base_stats()?

I tried adding them to rx and tx and mlx5e_get_base_stats (similar to what
mlx5e_fold_sw_stats64 does) and the test still fails.

Maybe something about the rtnl stats are what's off here and the queue
stats are fine?

FWIW: I spoke with the Mellanox folks off list several weeks ago and they
seemed to suggest skipping the PTP stats made the most sense.

I think at that time I didn't really understand get_base_stats that well,
so maybe we'd have come to a different conclusion then.

FWIW, here's what I tried and the rtnl vs qstat test still failed in
exactly the same way:

--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -5337,10 +5337,25 @@ static void mlx5e_get_base_stats(struct net_device *dev,
                rx->packets = 0;
                rx->bytes = 0;
                rx->alloc_fail = 0;
+               if (priv->rx_ptp_opened) {
+                       struct mlx5e_rq_stats *rq_stats = &priv->ptp_stats.rq;
+                       rx->packets = rq_stats->packets;
+                       rx->bytes = rq_stats->bytes;
+               }
        }

        tx->packets = 0;
        tx->bytes = 0;
+
+       if (priv->tx_ptp_opened) {
+               int i;
+               for (i = 0; i < priv->max_opened_tc; i++) {
+                       struct mlx5e_sq_stats *sq_stats = &priv->ptp_stats.sq[i];
+
+                       tx->packets    += sq_stats->packets;
+                       tx->bytes      += sq_stats->bytes;
+               }
+       }
 }

> We should probably touch up the kdoc a little bit, but it sounds like
> the sort of thing which would fall into the realm of "misc delta"
> values:
> 
> diff --git a/include/net/netdev_queues.h b/include/net/netdev_queues.h
> index c7ac4539eafc..f5d9f3ad5b66 100644
> --- a/include/net/netdev_queues.h
> +++ b/include/net/netdev_queues.h
> @@ -59,6 +59,8 @@ struct netdev_queue_stats_tx {
>   * statistics will not generally add up to the total number of events for
>   * the device. The @get_base_stats callback allows filling in the delta
>   * between events for currently live queues and overall device history.
> + * @get_base_stats can also be used to report any miscellaneous packets
> + * transferred outside of the main set of queues used by the networking stack.
>   * When the statistics for the entire device are queried, first @get_base_stats
>   * is issued to collect the delta, and then a series of per-queue callbacks.
>   * Only statistics which are set in @get_base_stats will be reported
> 
> 
> SG?

I think that sounds good and makes sense, yea. By that definition, then I
should leave the PTP stats as shown above. If you agree, I'll add that
to the v2.

I feel like I should probably wait before sending a v2 with PTP included in
get_base_stats to see if the Mellanox folks have any hints about why rtnl
!= queue stats on mlx5?

What do you think?