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Message-ID:
 <CH0PR12MB8580B042F111420724BD1625C9E72@CH0PR12MB8580.namprd12.prod.outlook.com>
Date: Fri, 10 May 2024 16:56:04 +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: RE: [PATCH net-next 2/2] virtio_net: Add TX stopped and wake
 counters

> From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> Sent: Friday, May 10, 2024 1:48 AM
> To: Dan Jurgens <danielj@...dia.com>
> Cc: mst@...hat.com; jasowang@...hat.com; virtualization@...ts.linux.dev;
> davem@...emloft.net; edumazet@...gle.com; kuba@...nel.org;
> pabeni@...hat.com; Jiri Pirko <jiri@...dia.com>; netdev@...r.kernel.org
> Subject: Re: RE: [PATCH net-next 2/2] virtio_net: Add TX stopped and wake
> counters
> 
> On Fri, 10 May 2024 03:35:51 +0000, Dan Jurgens <danielj@...dia.com>
> wrote:
> > > 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.
> 
> Here, we start the queue immediately after the queue is stopped.
> So for the upper layer, the queue "has not" changed the status, I think we do
> not need to update the wake counter.

I think we should. We incremented the stop counter. If they get out sync wake loses any functionality.

> 
> Thanks.
> 
> 
> >
> > >
> > > 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
> > > >
> >

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