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| author | Simon Schippers <simon.schippers@tu-dortmund.de> | 2026-07-28 11:22:37 +0200 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-07-29 17:12:26 -0700 |
| commit | f11b48aa674b475f196bede7d69593c050107fc5 (patch) | |
| tree | a02fd94a52cd7cf30c99bd1408227e6ffd315ce4 | |
| parent | 82f0e98ba302c30594e61c8f0d7a7908da78bd82 (diff) | |
| download | linux-next-f11b48aa674b475f196bede7d69593c050107fc5.tar.gz linux-next-f11b48aa674b475f196bede7d69593c050107fc5.zip | |
Revert "tun/tap & vhost-net: avoid ptr_ring tail-drop when a qdisc is present"
This reverts commit 1d6e569b7d0c0b2736636749e4be0a27f3cefcb3.
The commit stops the netdev queue when the ptr_ring is full instead of
dropping the packet. My own tests showed no relevant regression, but on
Brett Sheffield's librecast testbed an IPv6 multicast testcase got
slower. With 8 iperf3 TCP threads sending, the throughput dropped from
13.5 Gbit/s to 9.13 Gbit/s.
Reported-by: Brett Sheffield <brett@librecast.net>
Closes: https://lore.kernel.org/netdev/akVnoOYQOrt8k-Gu@karahi.librecast.net/
Signed-off-by: Simon Schippers <simon.schippers@tu-dortmund.de>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Link: https://patch.msgid.link/20260728092240.250257-2-simon.schippers@tu-dortmund.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | drivers/net/tun.c | 25 |
1 files changed, 2 insertions, 23 deletions
diff --git a/drivers/net/tun.c b/drivers/net/tun.c index ffbe6f13fb1f..ec5573f545af 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1018,7 +1018,6 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev) struct netdev_queue *queue; struct tun_file *tfile; int len = skb->len; - int ret; rcu_read_lock(); tfile = rcu_dereference(tun->tfiles[txq]); @@ -1073,33 +1072,13 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev) nf_reset_ct(skb); - queue = netdev_get_tx_queue(dev, txq); - - spin_lock(&tfile->tx_ring.producer_lock); - ret = __ptr_ring_produce(&tfile->tx_ring, skb); - if (!qdisc_txq_has_no_queue(queue) && - __ptr_ring_check_produce(&tfile->tx_ring) == -ENOSPC) { - netif_tx_stop_queue(queue); - /* Paired with smp_mb() in __tun_wake_queue() */ - smp_mb__after_atomic(); - if (!__ptr_ring_check_produce(&tfile->tx_ring)) - netif_tx_wake_queue(queue); - } - spin_unlock(&tfile->tx_ring.producer_lock); - - if (ret) { - /* This should be a rare case if a qdisc is present, but - * can happen due to lltx. - * Since skb_tx_timestamp(), skb_orphan(), - * run_ebpf_filter() and pskb_trim() could have tinkered - * with the SKB, returning NETDEV_TX_BUSY is unsafe and - * we must drop instead. - */ + if (ptr_ring_produce(&tfile->tx_ring, skb)) { drop_reason = SKB_DROP_REASON_FULL_RING; goto drop; } /* dev->lltx requires to do our own update of trans_start */ + queue = netdev_get_tx_queue(dev, txq); txq_trans_cond_update(queue); /* Notify and wake up reader process */ |