Messages in this thread | | | Date | Tue, 10 Apr 2012 17:10:41 +0300 | From | "Michael S. Tsirkin" <> | Subject | Re: [PATCH] net: orphan queued skbs if device tx can stall |
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On Tue, Apr 10, 2012 at 03:52:09PM +0200, Eric Dumazet wrote: > On Tue, 2012-04-10 at 15:41 +0300, Michael S. Tsirkin wrote: > > > I think it's a bad interface too but it's in a userspace ABI > > now so I suspect we are stuck with it for now. We can try deprecating > > but we can't just drop it. > > > > By the way, skb orphaning should already be done in skb_orphan_try(), > not sure why its done again in tun_net_xmit().
I think it's for when some tx flags are set.
> Note we perform orphaning right before giving skb to device on premise > it'll be sent (and freed) in a reasonable amount of time.
Right. No way to ensure this with tun :(
> With following patch, no more qdisc on top of tun device,
I'll test this, thanks.
> yet user can > change the limit
Question: if tun is moved between namespaces after tx queue len is changed, will it get a queueing qdisc then? If yes we need some other hack to address that ...
> (I would be curious to know if anybody changes tun > txqueuelen and why) > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > index bb8c72c..c4a00cf 100644 > --- a/drivers/net/tun.c > +++ b/drivers/net/tun.c > @@ -379,6 +379,7 @@ static int tun_net_close(struct net_device *dev) > static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev) > { > struct tun_struct *tun = netdev_priv(dev); > + int limit; > > tun_debug(KERN_INFO, tun, "tun_net_xmit %d\n", skb->len); > > @@ -396,7 +397,8 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev) > sk_filter(tun->socket.sk, skb)) > goto drop; > > - if (skb_queue_len(&tun->socket.sk->sk_receive_queue) >= dev->tx_queue_len) { > + limit = dev->tx_queue_len ? : TUN_READQ_SIZE; > + if (skb_queue_len(&tun->socket.sk->sk_receive_queue) >= limit) { > if (!(tun->flags & TUN_ONE_QUEUE)) { > /* Normal queueing mode. */ > /* Packet scheduler handles dropping of further packets. */ > @@ -521,7 +523,7 @@ static void tun_net_init(struct net_device *dev) > /* Zero header length */ > dev->type = ARPHRD_NONE; > dev->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST; > - dev->tx_queue_len = TUN_READQ_SIZE; /* We prefer our own queue length */ > + dev->tx_queue_len = 0; > break; > > case TUN_TAP_DEV: > @@ -532,7 +534,7 @@ static void tun_net_init(struct net_device *dev) > > eth_hw_addr_random(dev); > > - dev->tx_queue_len = TUN_READQ_SIZE; /* We prefer our own queue length */ > + dev->tx_queue_len = 0; > break; > } > } >
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