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

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Message-ID:
 <CH0PR12MB8580571225697B1ABDD55541C97D2@CH0PR12MB8580.namprd12.prod.outlook.com>
Date: Tue, 30 Jan 2024 15:43:48 +0000
From: Daniel Jurgens <danielj@...dia.com>
To: Heng Qi <hengqi@...ux.alibaba.com>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>
CC: "mst@...hat.com" <mst@...hat.com>, "jasowang@...hat.com"
	<jasowang@...hat.com>, "xuanzhuo@...ux.alibaba.com"
	<xuanzhuo@...ux.alibaba.com>, "virtualization@...ts.linux.dev"
	<virtualization@...ts.linux.dev>, "davem@...emloft.net"
	<davem@...emloft.net>, "edumazet@...gle.com" <edumazet@...gle.com>,
	"kuba@...nel.org" <kuba@...nel.org>, "abeni@...hat.com" <abeni@...hat.com>,
	Parav Pandit <parav@...dia.com>
Subject: RE: [PATCH net-next] virtio_net: Add TX stop and wake counters

> From: Heng Qi <hengqi@...ux.alibaba.com>
> Sent: Tuesday, January 30, 2024 9:17 AM
> 在 2024/1/30 下午10:25, Daniel Jurgens 写道:
> > 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@...dia.com>
> > Reviewed-by: Parav Pandit <parav@...dia.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;
> >   };
> 
> Hi Daniel!
> 
> tx_stop/wake only counts the status in the I/O path.
> Do the status of virtnet_config_changed_work and virtnet_tx_resize need to
> be counted?
> 

My motivation for the counter is detecting full TX queues. I don't think counting them in the control path is useful, but it can be done if you disagree.

> Thanks,
> Heng
> 
> >
> >   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);
> >