Re: [PATCH v2] virtio_net: enhance wake/stop tx queue statistics accounting

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Nov 20, 2025 at 09:53:20AM +0800, liming.wu@jaguarmicro.com wrote:
> From: Liming Wu <liming.wu@jaguarmicro.com>
> 
> This patch refines and strengthens the statistics collection of TX queue
> wake/stop events introduced by commit c39add9b2423 ("virtio_net: Add TX
> stopped and wake counters").
> 
> Previously, the driver only recorded partial wake/stop statistics
> for TX queues. Some wake events triggered by 'skb_xmit_done()' or resume
> operations were not counted, which made the per-queue metrics incomplete.
> 
> Signed-off-by: Liming Wu <liming.wu@jaguarmicro.com>

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> ---
>  drivers/net/virtio_net.c | 44 ++++++++++++++++++++++++----------------
>  1 file changed, 26 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 8e8a179aaa49..b714b190db2a 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -775,10 +775,26 @@ static bool virtqueue_napi_complete(struct napi_struct *napi,
>  	return false;
>  }
>  
> +static void virtnet_tx_wake_queue(struct virtnet_info *vi,
> +				struct send_queue *sq)
> +{
> +	unsigned int index = vq2txq(sq->vq);
> +	struct netdev_queue *txq = netdev_get_tx_queue(vi->dev, index);
> +
> +	if (netif_tx_queue_stopped(txq)) {
> +		u64_stats_update_begin(&sq->stats.syncp);
> +		u64_stats_inc(&sq->stats.wake);
> +		u64_stats_update_end(&sq->stats.syncp);
> +		netif_tx_wake_queue(txq);
> +	}
> +}
> +
>  static void skb_xmit_done(struct virtqueue *vq)
>  {
>  	struct virtnet_info *vi = vq->vdev->priv;
> -	struct napi_struct *napi = &vi->sq[vq2txq(vq)].napi;
> +	unsigned int index = vq2txq(vq);
> +	struct send_queue *sq = &vi->sq[index];
> +	struct napi_struct *napi = &sq->napi;
>  
>  	/* Suppress further interrupts. */
>  	virtqueue_disable_cb(vq);
> @@ -786,8 +802,7 @@ static void skb_xmit_done(struct virtqueue *vq)
>  	if (napi->weight)
>  		virtqueue_napi_schedule(napi, vq);
>  	else
> -		/* We were probably waiting for more output buffers. */
> -		netif_wake_subqueue(vi->dev, vq2txq(vq));
> +		virtnet_tx_wake_queue(vi, sq);
>  }
>  
>  #define MRG_CTX_HEADER_SHIFT 22
> @@ -3068,13 +3083,8 @@ static void virtnet_poll_cleantx(struct receive_queue *rq, int budget)
>  			free_old_xmit(sq, txq, !!budget);
>  		} while (unlikely(!virtqueue_enable_cb_delayed(sq->vq)));
>  
> -		if (sq->vq->num_free >= MAX_SKB_FRAGS + 2 &&
> -		    netif_tx_queue_stopped(txq)) {
> -			u64_stats_update_begin(&sq->stats.syncp);
> -			u64_stats_inc(&sq->stats.wake);
> -			u64_stats_update_end(&sq->stats.syncp);
> -			netif_tx_wake_queue(txq);
> -		}
> +		if (sq->vq->num_free >= MAX_SKB_FRAGS + 2)
> +			virtnet_tx_wake_queue(vi, sq);
>  
>  		__netif_tx_unlock(txq);
>  	}
> @@ -3264,13 +3274,8 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget)
>  	else
>  		free_old_xmit(sq, txq, !!budget);
>  
> -	if (sq->vq->num_free >= MAX_SKB_FRAGS + 2 &&
> -	    netif_tx_queue_stopped(txq)) {
> -		u64_stats_update_begin(&sq->stats.syncp);
> -		u64_stats_inc(&sq->stats.wake);
> -		u64_stats_update_end(&sq->stats.syncp);
> -		netif_tx_wake_queue(txq);
> -	}
> +	if (sq->vq->num_free >= MAX_SKB_FRAGS + 2)
> +		virtnet_tx_wake_queue(vi, sq);
>  
>  	if (xsk_done >= budget) {
>  		__netif_tx_unlock(txq);
> @@ -3521,6 +3526,9 @@ static void virtnet_tx_pause(struct virtnet_info *vi, struct send_queue *sq)
>  
>  	/* Prevent the upper layer from trying to send packets. */
>  	netif_stop_subqueue(vi->dev, qindex);
> +	u64_stats_update_begin(&sq->stats.syncp);
> +	u64_stats_inc(&sq->stats.stop);
> +	u64_stats_update_end(&sq->stats.syncp);
>  
>  	__netif_tx_unlock_bh(txq);
>  }
> @@ -3537,7 +3545,7 @@ static void virtnet_tx_resume(struct virtnet_info *vi, struct send_queue *sq)
>  
>  	__netif_tx_lock_bh(txq);
>  	sq->reset = false;
> -	netif_tx_wake_queue(txq);
> +	virtnet_tx_wake_queue(vi, sq);
>  	__netif_tx_unlock_bh(txq);
>  
>  	if (running)
> -- 
> 2.34.1