Re: [PATCH net-next] net: dsa: Add support for 64-bit statistics

[Florian Fainelli <f.fainelli@gmail.com>]

On 08/01/2017 03:00 PM, Florian Fainelli wrote:
> DSA slave network devices maintain a pair of bytes and packets counters
> for each directions, but these are not 64-bit capable. Re-use
> pcpu_sw_netstats which contains exactly what we need for that purpose
> and update the code path to report 64-bit capable statistics.

Humm, I do see a long time for ifconfig/ethtool -S to complete after
having transfered over 250GiB of data, the locking looks correct to me
in that statistics for the RX path are updated from softIRQ context
(napi_gro_receive/netif_receive_skb) but maybe I did misunderstand
whether the softirq/IRQ context applies to the producer and not the
reader...

> 
> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> ---
>  net/dsa/dsa.c      |  8 ++++++--
>  net/dsa/dsa_priv.h |  2 ++
>  net/dsa/slave.c    | 38 +++++++++++++++++++++++++++++++-------
>  3 files changed, 39 insertions(+), 9 deletions(-)
> 
> diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
> index a55e2e4087a4..0ba842c08dd3 100644
> --- a/net/dsa/dsa.c
> +++ b/net/dsa/dsa.c
> @@ -190,6 +190,7 @@ static int dsa_switch_rcv(struct sk_buff *skb, struct net_device *dev,
>  {
>  	struct dsa_switch_tree *dst = dev->dsa_ptr;
>  	struct sk_buff *nskb = NULL;
> +	struct dsa_slave_priv *p;
>  
>  	if (unlikely(dst == NULL)) {
>  		kfree_skb(skb);
> @@ -207,12 +208,15 @@ static int dsa_switch_rcv(struct sk_buff *skb, struct net_device *dev,
>  	}
>  
>  	skb = nskb;
> +	p = netdev_priv(skb->dev);
>  	skb_push(skb, ETH_HLEN);
>  	skb->pkt_type = PACKET_HOST;
>  	skb->protocol = eth_type_trans(skb, skb->dev);
>  
> -	skb->dev->stats.rx_packets++;
> -	skb->dev->stats.rx_bytes += skb->len;
> +	u64_stats_update_begin(&p->stats64.syncp);
> +	p->stats64.rx_packets++;
> +	p->stats64.rx_bytes += skb->len;
> +	u64_stats_update_end(&p->stats64.syncp);
>  
>  	netif_receive_skb(skb);
>  
> diff --git a/net/dsa/dsa_priv.h b/net/dsa/dsa_priv.h
> index 55982cc39b24..7aa0656296c2 100644
> --- a/net/dsa/dsa_priv.h
> +++ b/net/dsa/dsa_priv.h
> @@ -77,6 +77,8 @@ struct dsa_slave_priv {
>  	struct sk_buff *	(*xmit)(struct sk_buff *skb,
>  					struct net_device *dev);
>  
> +	struct pcpu_sw_netstats	stats64;
> +
>  	/* DSA port data, such as switch, port index, etc. */
>  	struct dsa_port		*dp;
>  
> diff --git a/net/dsa/slave.c b/net/dsa/slave.c
> index 9507bd38cf04..65f3cef85976 100644
> --- a/net/dsa/slave.c
> +++ b/net/dsa/slave.c
> @@ -354,8 +354,10 @@ static netdev_tx_t dsa_slave_xmit(struct sk_buff *skb, struct net_device *dev)
>  	struct dsa_slave_priv *p = netdev_priv(dev);
>  	struct sk_buff *nskb;
>  
> -	dev->stats.tx_packets++;
> -	dev->stats.tx_bytes += skb->len;
> +	u64_stats_update_begin(&p->stats64.syncp);
> +	p->stats64.tx_packets++;
> +	p->stats64.tx_bytes += skb->len;
> +	u64_stats_update_end(&p->stats64.syncp);
>  
>  	/* Transmit function may have to reallocate the original SKB,
>  	 * in which case it must have freed it. Only free it here on error.
> @@ -594,11 +596,15 @@ static void dsa_slave_get_ethtool_stats(struct net_device *dev,
>  {
>  	struct dsa_slave_priv *p = netdev_priv(dev);
>  	struct dsa_switch *ds = p->dp->ds;
> -
> -	data[0] = dev->stats.tx_packets;
> -	data[1] = dev->stats.tx_bytes;
> -	data[2] = dev->stats.rx_packets;
> -	data[3] = dev->stats.rx_bytes;
> +	unsigned int start;
> +
> +	do {
> +		start = u64_stats_fetch_begin_irq(&p->stats64.syncp);
> +		data[0] = p->stats64.tx_packets;
> +		data[1] = p->stats64.tx_bytes;
> +		data[2] = p->stats64.rx_packets;
> +		data[3] = p->stats64.rx_bytes;
> +	} while (u64_stats_fetch_retry_irq(&p->stats64.syncp, start));
>  	if (ds->ops->get_ethtool_stats)
>  		ds->ops->get_ethtool_stats(ds, p->dp->index, data + 4);
>  }
> @@ -861,6 +867,22 @@ static int dsa_slave_setup_tc(struct net_device *dev, u32 handle,
>  	}
>  }
>  
> +static void dsa_slave_get_stats64(struct net_device *dev,
> +				  struct rtnl_link_stats64 *stats)
> +{
> +	struct dsa_slave_priv *p = netdev_priv(dev);
> +	unsigned int start;
> +
> +	netdev_stats_to_stats64(stats, &dev->stats);
> +	do {
> +		start = u64_stats_fetch_begin_irq(&p->stats64.syncp);
> +		stats->tx_packets = p->stats64.tx_packets;
> +		stats->tx_bytes = p->stats64.tx_bytes;
> +		stats->rx_packets = p->stats64.rx_packets;
> +		stats->rx_bytes = p->stats64.rx_bytes;
> +	} while (u64_stats_fetch_retry_irq(&p->stats64.syncp, start));
> +}
> +
>  void dsa_cpu_port_ethtool_init(struct ethtool_ops *ops)
>  {
>  	ops->get_sset_count = dsa_cpu_port_get_sset_count;
> @@ -936,6 +958,7 @@ static const struct net_device_ops dsa_slave_netdev_ops = {
>  	.ndo_bridge_dellink	= switchdev_port_bridge_dellink,
>  	.ndo_get_phys_port_name	= dsa_slave_get_phys_port_name,
>  	.ndo_setup_tc		= dsa_slave_setup_tc,
> +	.ndo_get_stats64	= dsa_slave_get_stats64,
>  };
>  
>  static const struct switchdev_ops dsa_slave_switchdev_ops = {
> @@ -1171,6 +1194,7 @@ int dsa_slave_create(struct dsa_switch *ds, struct device *parent,
>  	slave_dev->vlan_features = master->vlan_features;
>  
>  	p = netdev_priv(slave_dev);
> +	u64_stats_init(&p->stats64.syncp);
>  	p->dp = &ds->ports[port];
>  	INIT_LIST_HEAD(&p->mall_tc_list);
>  	p->xmit = dst->tag_ops->xmit;
> 


-- 
Florian