diff options
| author | Jakub Kicinski <kuba@kernel.org> | 2026-07-29 17:12:29 -0700 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-07-29 17:12:29 -0700 |
| commit | 7e107ab85cd40752a06e1788e10b0692fb021cbf (patch) | |
| tree | 773294ab263a174511803aacfcf1442ec8c9676f /include | |
| parent | 82f0e98ba302c30594e61c8f0d7a7908da78bd82 (diff) | |
| parent | c3da92af07eaba43f49910b2e4fbd016e563fa35 (diff) | |
Merge branch 'revert-tun-tap-vhost-net-apply-qdisc-backpressure-on-full-ptr_ring-to-reduce-tx-drops'
Simon Schippers says:
====================
Revert "tun/tap & vhost-net: apply qdisc backpressure on full ptr_ring to reduce TX drops"
Commit 1d6e569b7d0c ("tun/tap & vhost-net: avoid ptr_ring tail-drop when
a qdisc is present") did not show a relevant performance regression in my
testing, but on Brett Sheffield's librecast testbed it causes a
significant throughput drop in an IPv6 multicast testcase. The regression
can be pinpointed to multiple iperf3 TCP threads sending: for 8 threads
the throughput dropped from 13.5 Gbit/s to 9.13 Gbit/s.
Therefore this series reverts the qdisc backpressure work.
Making the backpressure opt-in via a new IFF_BACKPRESSURE flag was
proposed in [1], but a new IFF_* flag needs more review scrutiny than is
available at the moment, so a revert was requested instead. The opt-in
will be resubmitted for net-next later.
[1] Link: https://lore.kernel.org/netdev/20260709095511.168235-1-simon.schippers@tu-dortmund.de/
Reported-by: Brett Sheffield <brett@librecast.net>
Closes: https://lore.kernel.org/netdev/akVnoOYQOrt8k-Gu@karahi.librecast.net/
====================
Link: https://patch.msgid.link/20260728092240.250257-1-simon.schippers@tu-dortmund.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/if_tun.h | 3 | ||||
| -rw-r--r-- | include/linux/ptr_ring.h | 20 |
2 files changed, 2 insertions, 21 deletions
diff --git a/include/linux/if_tun.h b/include/linux/if_tun.h index 5f3e206c7a73..80166eb62f41 100644 --- a/include/linux/if_tun.h +++ b/include/linux/if_tun.h @@ -22,7 +22,6 @@ struct tun_msg_ctl { #if defined(CONFIG_TUN) || defined(CONFIG_TUN_MODULE) struct socket *tun_get_socket(struct file *); struct ptr_ring *tun_get_tx_ring(struct file *file); -void tun_wake_queue(struct file *file, int consumed); static inline bool tun_is_xdp_frame(void *ptr) { @@ -56,8 +55,6 @@ static inline struct ptr_ring *tun_get_tx_ring(struct file *f) return ERR_PTR(-EINVAL); } -static inline void tun_wake_queue(struct file *f, int consumed) {} - static inline bool tun_is_xdp_frame(void *ptr) { return false; diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h index c95e891903f0..d2c3629bbe45 100644 --- a/include/linux/ptr_ring.h +++ b/include/linux/ptr_ring.h @@ -98,29 +98,13 @@ static inline bool ptr_ring_full_bh(struct ptr_ring *r) /* Note: callers invoking this in a loop must use a compiler barrier, * for example cpu_relax(). Callers must hold producer_lock. - */ -static inline int __ptr_ring_check_produce(struct ptr_ring *r) -{ - if (unlikely(!r->size)) - return -EINVAL; - - if (data_race(r->queue[r->producer])) - return -ENOSPC; - - return 0; -} - -/* Note: callers invoking this in a loop must use a compiler barrier, - * for example cpu_relax(). Callers must hold producer_lock. * Callers are responsible for making sure pointer that is being queued * points to a valid data. */ static inline int __ptr_ring_produce(struct ptr_ring *r, void *ptr) { - int p = __ptr_ring_check_produce(r); - - if (p) - return p; + if (unlikely(!r->size) || data_race(r->queue[r->producer])) + return -ENOSPC; /* Make sure the pointer we are storing points to a valid data. */ /* Pairs with the dependency ordering in __ptr_ring_consume. */ |