[PATCH net-next] virtio_net: Add TX stop and wake counters

[Daniel Jurgens <danielj@nvidia.com>]

Add a tx queue stop and wake counters, they are useful for debugging.

	$ ethtool -S ens5f2 | grep 'tx_stop\|tx_wake'
	...
	tx_queue_1_tx_stop: 16726
	tx_queue_1_tx_wake: 16726
	...
	tx_queue_8_tx_stop: 1500110
	tx_queue_8_tx_wake: 1500110

Signed-off-by: Daniel Jurgens <danielj@nvidia.com>
Reviewed-by: Parav Pandit <parav@nvidia.com>
---
 drivers/net/virtio_net.c | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 3cb8aa193884..7e3c31ceaf7e 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -88,6 +88,8 @@ struct virtnet_sq_stats {
 	u64_stats_t xdp_tx_drops;
 	u64_stats_t kicks;
 	u64_stats_t tx_timeouts;
+	u64_stats_t tx_stop;
+	u64_stats_t tx_wake;
 };
 
 struct virtnet_rq_stats {
@@ -112,6 +114,8 @@ static const struct virtnet_stat_desc virtnet_sq_stats_desc[] = {
 	{ "xdp_tx_drops",	VIRTNET_SQ_STAT(xdp_tx_drops) },
 	{ "kicks",		VIRTNET_SQ_STAT(kicks) },
 	{ "tx_timeouts",	VIRTNET_SQ_STAT(tx_timeouts) },
+	{ "tx_stop",		VIRTNET_SQ_STAT(tx_stop) },
+	{ "tx_wake",		VIRTNET_SQ_STAT(tx_wake) },
 };
 
 static const struct virtnet_stat_desc virtnet_rq_stats_desc[] = {
@@ -843,6 +847,9 @@ static void check_sq_full_and_disable(struct virtnet_info *vi,
 	 */
 	if (sq->vq->num_free < 2+MAX_SKB_FRAGS) {
 		netif_stop_subqueue(dev, qnum);
+		u64_stats_update_begin(&sq->stats.syncp);
+		u64_stats_inc(&sq->stats.tx_stop);
+		u64_stats_update_end(&sq->stats.syncp);
 		if (use_napi) {
 			if (unlikely(!virtqueue_enable_cb_delayed(sq->vq)))
 				virtqueue_napi_schedule(&sq->napi, sq->vq);
@@ -851,6 +858,9 @@ static void check_sq_full_and_disable(struct virtnet_info *vi,
 			free_old_xmit_skbs(sq, false);
 			if (sq->vq->num_free >= 2+MAX_SKB_FRAGS) {
 				netif_start_subqueue(dev, qnum);
+				u64_stats_update_begin(&sq->stats.syncp);
+				u64_stats_inc(&sq->stats.tx_wake);
+				u64_stats_update_end(&sq->stats.syncp);
 				virtqueue_disable_cb(sq->vq);
 			}
 		}
@@ -2163,8 +2173,14 @@ static void virtnet_poll_cleantx(struct receive_queue *rq)
 			free_old_xmit_skbs(sq, true);
 		} while (unlikely(!virtqueue_enable_cb_delayed(sq->vq)));
 
-		if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS)
+		if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) {
+			if (netif_tx_queue_stopped(txq)) {
+				u64_stats_update_begin(&sq->stats.syncp);
+				u64_stats_inc(&sq->stats.tx_wake);
+				u64_stats_update_end(&sq->stats.syncp);
+			}
 			netif_tx_wake_queue(txq);
+		}
 
 		__netif_tx_unlock(txq);
 	}
@@ -2310,8 +2326,14 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget)
 	virtqueue_disable_cb(sq->vq);
 	free_old_xmit_skbs(sq, true);
 
-	if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS)
+	if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) {
+		if (netif_tx_queue_stopped(txq)) {
+			u64_stats_update_begin(&sq->stats.syncp);
+			u64_stats_inc(&sq->stats.tx_wake);
+			u64_stats_update_end(&sq->stats.syncp);
+		}
 		netif_tx_wake_queue(txq);
+	}
 
 	opaque = virtqueue_enable_cb_prepare(sq->vq);
 
-- 
2.42.0