netdev - RE: [PATCH net-next 2/2] virtio_net: Add TX stopped and wake counters

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Message-ID:
 <CH0PR12MB858086B1DEB3F5D4015D937EC9E72@CH0PR12MB8580.namprd12.prod.outlook.com>
Date: Fri, 10 May 2024 03:35:51 +0000
From: Dan Jurgens <danielj@...dia.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
CC: "mst@...hat.com" <mst@...hat.com>, "jasowang@...hat.com"
	<jasowang@...hat.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>, "pabeni@...hat.com" <pabeni@...hat.com>,
	Jiri Pirko <jiri@...dia.com>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>
Subject: RE: [PATCH net-next 2/2] virtio_net: Add TX stopped and wake counters

> From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> Sent: Thursday, May 9, 2024 8:22 PM
> To: Dan Jurgens <danielj@...dia.com>
> Cc: mst@...hat.com; jasowang@...hat.com; xuanzhuo@...ux.alibaba.com;
> virtualization@...ts.linux.dev; davem@...emloft.net;
> edumazet@...gle.com; kuba@...nel.org; pabeni@...hat.com; Jiri Pirko
> <jiri@...dia.com>; Dan Jurgens <danielj@...dia.com>;
> netdev@...r.kernel.org
> Subject: Re: [PATCH net-next 2/2] virtio_net: Add TX stopped and wake
> counters
> 
> On Thu, 9 May 2024 11:32:16 -0500, Daniel Jurgens <danielj@...dia.com>
> wrote:
> > Add a tx queue stop and wake counters, they are useful for debugging.
> >
> > $ ./tools/net/ynl/cli.py --spec netlink/specs/netdev.yaml \ --dump
> > qstats-get --json '{"scope": "queue"}'
> > ...
> >  {'ifindex': 13,
> >   'queue-id': 0,
> >   'queue-type': 'tx',
> >   'tx-bytes': 14756682850,
> >   'tx-packets': 226465,
> >   'tx-stop': 113208,
> >   'tx-wake': 113208},
> >  {'ifindex': 13,
> >   'queue-id': 1,
> >   'queue-type': 'tx',
> >   'tx-bytes': 18167675008,
> >   'tx-packets': 278660,
> >   'tx-stop': 8632,
> >   'tx-wake': 8632}]
> >
> > Signed-off-by: Daniel Jurgens <danielj@...dia.com>
> > Reviewed-by: Jiri Pirko <jiri@...dia.com>
> > ---
> >  drivers/net/virtio_net.c | 28 ++++++++++++++++++++++++++--
> >  1 file changed, 26 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index
> > 218a446c4c27..df6121c38a1b 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -95,6 +95,8 @@ struct virtnet_sq_stats {
> >  	u64_stats_t xdp_tx_drops;
> >  	u64_stats_t kicks;
> >  	u64_stats_t tx_timeouts;
> > +	u64_stats_t stop;
> > +	u64_stats_t wake;
> >  };
> >
> >  struct virtnet_rq_stats {
> > @@ -145,6 +147,8 @@ static const struct virtnet_stat_desc
> > virtnet_rq_stats_desc[] = {  static const struct virtnet_stat_desc
> virtnet_sq_stats_desc_qstat[] = {
> >  	VIRTNET_SQ_STAT_QSTAT("packets", packets),
> >  	VIRTNET_SQ_STAT_QSTAT("bytes",   bytes),
> > +	VIRTNET_SQ_STAT_QSTAT("stop",	 stop),
> > +	VIRTNET_SQ_STAT_QSTAT("wake",	 wake),
> >  };
> >
> >  static const struct virtnet_stat_desc virtnet_rq_stats_desc_qstat[] =
> > { @@ -1014,6 +1018,9 @@ 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.stop);
> > +		u64_stats_update_end(&sq->stats.syncp);
> 
> How about introduce two helpers to wrap
> netif_tx_queue_stopped and netif_start_subqueue?
> 
> >  		if (use_napi) {
> >  			if (unlikely(!virtqueue_enable_cb_delayed(sq->vq)))
> >  				virtqueue_napi_schedule(&sq->napi, sq-
> >vq); @@ -1022,6 +1029,9 @@
> > static void check_sq_full_and_disable(struct virtnet_info *vi,
> >  			free_old_xmit(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.wake);
> > +				u64_stats_update_end(&sq->stats.syncp);
> 
> If we start the queue immediately, should we update the counter?

I intentionally only counted the wakes on restarts after stopping the queue.
I don't think counting the initial wake adds any value since it always happens.

> 
> Thanks.
> 
> >  				virtqueue_disable_cb(sq->vq);
> >  			}
> >  		}
> > @@ -2322,8 +2332,14 @@ static void virtnet_poll_cleantx(struct
> receive_queue *rq)
> >  			free_old_xmit(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.wake);
> > +				u64_stats_update_end(&sq->stats.syncp);
> > +			}
> >  			netif_tx_wake_queue(txq);
> > +		}
> >
> >  		__netif_tx_unlock(txq);
> >  	}
> > @@ -2473,8 +2489,14 @@ static int virtnet_poll_tx(struct napi_struct
> *napi, int budget)
> >  	virtqueue_disable_cb(sq->vq);
> >  	free_old_xmit(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.wake);
> > +			u64_stats_update_end(&sq->stats.syncp);
> > +		}
> >  		netif_tx_wake_queue(txq);
> > +	}
> >
> >  	opaque = virtqueue_enable_cb_prepare(sq->vq);
> >
> > @@ -4790,6 +4812,8 @@ static void virtnet_get_base_stats(struct
> > net_device *dev,
> >
> >  	tx->bytes = 0;
> >  	tx->packets = 0;
> > +	tx->stop = 0;
> > +	tx->wake = 0;
> >
> >  	if (vi->device_stats_cap & VIRTIO_NET_STATS_TYPE_TX_BASIC) {
> >  		tx->hw_drops = 0;
> > --
> > 2.44.0
> >