netdev - Re: [PATCH] virtio_net: introduce TX timeout watchdog

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Date:   Sun, 26 Sep 2021 12:36:10 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     tonylu_linux <tonylu@...ux.alibaba.com>
Cc:     mst <mst@...hat.com>, linux-kernel <linux-kernel@...r.kernel.org>,
        davem <davem@...emloft.net>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] virtio_net: introduce TX timeout watchdog

On Fri, Sep 17, 2021 at 4:45 PM tonylu_linux <tonylu@...ux.alibaba.com> wrote:
>
> From: Tony Lu <tony.ly@...ux.alibaba.com>
>
> This implements ndo_tx_timeout handler and put this into stats. When
> there is something wrong to send out packets, we could notice tx timeout
> events and total timeout counter.
>
> We have suffered send timeout issues due to the backends hung. With this,
> we can find the details, and collect the counters by monitor systems.
>
> Signed-off-by: Tony Lu <tony.ly@...ux.alibaba.com>

Note that we support non tx interrupt mode (which could be turned on
via ethtool).

I wonder if this can work well in that case.

Or maybe it's the time to remove the non tx interrupt mode completely.
Want to do that?

Thanks

> ---
>  drivers/net/virtio_net.c | 22 +++++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 271d38c1d9f8..90fed0fdc40f 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -80,6 +80,7 @@ struct virtnet_sq_stats {
>         u64 xdp_tx;
>         u64 xdp_tx_drops;
>         u64 kicks;
> +       u64 tx_timeouts;
>  };
>
>  struct virtnet_rq_stats {
> @@ -103,6 +104,7 @@ static const struct virtnet_stat_desc virtnet_sq_stats_desc[] = {
>         { "xdp_tx",             VIRTNET_SQ_STAT(xdp_tx) },
>         { "xdp_tx_drops",       VIRTNET_SQ_STAT(xdp_tx_drops) },
>         { "kicks",              VIRTNET_SQ_STAT(kicks) },
> +       { "tx_timeouts",        VIRTNET_SQ_STAT(tx_timeouts) },
>  };
>
>  static const struct virtnet_stat_desc virtnet_rq_stats_desc[] = {
> @@ -1856,7 +1858,7 @@ static void virtnet_stats(struct net_device *dev,
>         int i;
>
>         for (i = 0; i < vi->max_queue_pairs; i++) {
> -               u64 tpackets, tbytes, rpackets, rbytes, rdrops;
> +               u64 tpackets, tbytes, terrors, rpackets, rbytes, rdrops;
>                 struct receive_queue *rq = &vi->rq[i];
>                 struct send_queue *sq = &vi->sq[i];
>
> @@ -1864,6 +1866,7 @@ static void virtnet_stats(struct net_device *dev,
>                         start = u64_stats_fetch_begin_irq(&sq->stats.syncp);
>                         tpackets = sq->stats.packets;
>                         tbytes   = sq->stats.bytes;
> +                       terrors  = sq->stats.tx_timeouts;
>                 } while (u64_stats_fetch_retry_irq(&sq->stats.syncp, start));
>
>                 do {
> @@ -1878,6 +1881,7 @@ static void virtnet_stats(struct net_device *dev,
>                 tot->rx_bytes   += rbytes;
>                 tot->tx_bytes   += tbytes;
>                 tot->rx_dropped += rdrops;
> +               tot->tx_errors  += terrors;
>         }
>
>         tot->tx_dropped = dev->stats.tx_dropped;
> @@ -2659,6 +2663,21 @@ static int virtnet_set_features(struct net_device *dev,
>         return 0;
>  }
>
> +static void virtnet_tx_timeout(struct net_device *dev, unsigned int txqueue)
> +{
> +       struct virtnet_info *priv = netdev_priv(dev);
> +       struct send_queue *sq = &priv->sq[txqueue];
> +       struct netdev_queue *txq = netdev_get_tx_queue(dev, txqueue);
> +
> +       u64_stats_update_begin(&sq->stats.syncp);
> +       sq->stats.tx_timeouts++;
> +       u64_stats_update_end(&sq->stats.syncp);
> +
> +       netdev_err(dev, "TX timeout on queue: %u, sq: %s, vq: 0x%x, name: %s, %u usecs ago\n",
> +                  txqueue, sq->name, sq->vq->index, sq->vq->name,
> +                  jiffies_to_usecs(jiffies - txq->trans_start));
> +}
> +
>  static const struct net_device_ops virtnet_netdev = {
>         .ndo_open            = virtnet_open,
>         .ndo_stop            = virtnet_close,
> @@ -2674,6 +2693,7 @@ static const struct net_device_ops virtnet_netdev = {
>         .ndo_features_check     = passthru_features_check,
>         .ndo_get_phys_port_name = virtnet_get_phys_port_name,
>         .ndo_set_features       = virtnet_set_features,
> +       .ndo_tx_timeout         = virtnet_tx_timeout,
>  };
>
>  static void virtnet_config_changed_work(struct work_struct *work)
> --
> 2.19.1.6.gb485710b
>