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From: Jakub Kicinski <kuba@kernel.org>
To: Heiner Kallweit <hkallweit1@gmail.com>
Cc: Willem de Bruijn <willemb@google.com>,
	David Miller <davem@davemloft.net>,
	Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
	Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
	Andrew Lunn <andrew@lunn.ch>,
	Vivien Didelot <vivien.didelot@gmail.com>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Vladimir Oltean <olteanv@gmail.com>,
	Russell King <linux@armlinux.org.uk>,
	Pablo Neira Ayuso <pablo@netfilter.org>,
	Harald Welte <laforge@gnumonks.org>,
	"Jason A. Donenfeld" <Jason@zx2c4.com>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	osmocom-net-gprs@lists.osmocom.org, wireguard@lists.zx2c4.com,
	Steffen Klassert <steffen.klassert@secunet.com>
Subject: Re: [PATCH net-next v2 03/10] tun: switch to net core provided statistics counters
Date: Fri, 6 Nov 2020 08:18:46 -0800
Message-ID: <20201106081846.27212e9e@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> (raw)
In-Reply-To: <aea7d78e-2d77-1f8a-70f0-73d46c96b44e@gmail.com>

On Fri, 6 Nov 2020 09:27:45 +0100 Heiner Kallweit wrote:
> On 06.11.2020 08:48, Heiner Kallweit wrote:
> > On 06.11.2020 02:14, Jakub Kicinski wrote:  
> >> On Wed, 4 Nov 2020 15:25:24 +0100 Heiner Kallweit wrote:  
> >>> @@ -1066,7 +1054,7 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
> >>>  	return NETDEV_TX_OK;
> >>>  
> >>>  drop:
> >>> -	this_cpu_inc(tun->pcpu_stats->tx_dropped);
> >>> +	dev->stats.tx_dropped++;
> >>>  	skb_tx_error(skb);
> >>>  	kfree_skb(skb);
> >>>  	rcu_read_unlock();  
> >>
> >> This is no longer atomic. Multiple CPUs may try to update it at the
> >> same time.
> >>
> >> Do you know what the story on dev->rx_dropped is? The kdoc says drivers
> >> are not supposed to use it but:
> >>
> >> drivers/net/ipvlan/ipvlan_core.c:               atomic_long_inc(&skb->dev->rx_dropped);
> >> drivers/net/macvlan.c:  atomic_long_inc(&skb->dev->rx_dropped);
> >> drivers/net/vxlan.c:            atomic_long_inc(&vxlan->dev->rx_dropped);
> >>
> >> Maybe tun can use it, too?
> >>  
> > Thanks, yes that should be possible. Here we speak about tx_dropped,
> > but AFAICS the same applies as for rx_dropped. Will change it accordingly
> > in a v3.
> >   
> For rx_dropped and tx_dropped it's easy, however tun also has a per-cpu
> counter for rx_frame_errors that is incremented if virtio_net_hdr_to_skb()
> fails. Not sure how to deal best with this one.

Umpf, yeah, so I'd probably add an atomic long to struct tun_struct,
but then you'll need to keep the ndo implementation instead of using
dev_get_tstats64 directly. I can't think of a better way, tho.

  reply	other threads:[~2020-11-06 16:19 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-04 14:23 [PATCH net-next v2 00/10] net: add and use dev_get_tstats64 Heiner Kallweit
2020-11-04 14:24 ` [PATCH net-next v2 01/10] net: core: add dev_get_tstats64 as a ndo_get_stats64 implementation Heiner Kallweit
2020-11-04 14:24 ` [PATCH net-next v2 02/10] net: dsa: use net core stats64 handling Heiner Kallweit
2020-11-04 14:25 ` [PATCH net-next v2 03/10] tun: switch to net core provided statistics counters Heiner Kallweit
2020-11-06  1:14   ` Jakub Kicinski
2020-11-06  7:48     ` Heiner Kallweit
2020-11-06  8:27       ` Heiner Kallweit
2020-11-06 16:18         ` Jakub Kicinski [this message]
2020-11-04 14:26 ` [PATCH net-next v2 04/10] ip6_tunnel: switch to dev_get_tstats64 Heiner Kallweit
2020-11-04 14:27 ` [PATCH net-next v2 05/10] net: " Heiner Kallweit
2020-11-04 14:27 ` [PATCH net-next v2 06/10] gtp: " Heiner Kallweit
2020-11-05  7:58   ` Harald Welte
2020-11-04 14:28 ` [PATCH net-next v2 07/10] wireguard: " Heiner Kallweit
2020-11-04 19:46   ` Jason A. Donenfeld
2020-11-04 14:28 ` [PATCH net-next v2 08/10] vti: " Heiner Kallweit
2020-11-04 14:29 ` [PATCH net-next v2 09/10] ipv4/ipv6: " Heiner Kallweit
2020-11-04 14:31 ` [PATCH net-next v2 10/10] net: remove ip_tunnel_get_stats64 Heiner Kallweit

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