[PATCH net-next 2/7] net_sched: sch_fq: clear past skb->tstamp if offloading pacing
From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date: 2026-07-06 13:34:41
Subsystem:
networking [general], tc subsystem, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Jamal Hadi Salim, Jiri Pirko, Linus Torvalds
From: Willem de Bruijn <willemb@google.com> When hardware offload is enabled, FQ will forward packets to the netdevice for pacing. The device has to test that skb->tstamp is in the future. Avoid this cost for packets whose txtime has already passed, by clearing skb->tstamp. Also disable timer drift logic when offload is enabled, because time_next_packet can exceed now causing a negative value. Signed-off-by: Willem de Bruijn <willemb@google.com> --- Sashiko, ignore pre-existing issues. In particular, effects on non-EDT packets and when queue or sk rate limit is set. Sashiko, pacing offload is an optimization. Ignore that some packets may not get offloaded, e.g., when txtime is a few usec in the future. --- net/sched/sch_fq.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-)
diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index d4cc8bc9fa06..36006f69a875 100644
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c@@ -399,6 +399,11 @@ static struct fq_flow *fq_classify(struct Qdisc *sch, struct sk_buff *skb, READ_ONCE(sk->sk_pacing_status) != SK_PACING_FQ) smp_store_release(&sk->sk_pacing_status, SK_PACING_FQ); + + if (q->offload_horizon && + fq_skb_cb(skb)->time_to_send <= now) + skb->tstamp = 0; + return &q->internal; }
@@ -707,6 +712,7 @@ static struct sk_buff *fq_dequeue(struct Qdisc *sch) struct fq_sched_data *q = qdisc_priv(sch); struct fq_perband_flows *pband; struct fq_flow_head *head; + u64 time_next_packet; struct sk_buff *skb; struct fq_flow *f; unsigned long rate;
@@ -721,7 +727,7 @@ static struct sk_buff *fq_dequeue(struct Qdisc *sch) if (skb) { q->internal.qlen--; fq_dequeue_skb(sch, &q->internal, skb); - goto out; + return skb; } now = ktime_get_ns();
@@ -758,8 +764,8 @@ static struct sk_buff *fq_dequeue(struct Qdisc *sch) skb = fq_peek(f); if (skb) { - u64 time_next_packet = max_t(u64, fq_skb_cb(skb)->time_to_send, - f->time_next_packet); + time_next_packet = max_t(u64, fq_skb_cb(skb)->time_to_send, + f->time_next_packet); if (now + q->offload_horizon < time_next_packet) { head->first = f->next;
@@ -828,11 +834,15 @@ static struct sk_buff *fq_dequeue(struct Qdisc *sch) * f->time_next_packet was set when prior packet was sent, * and current time (@now) can be too late by tens of us. */ - if (f->time_next_packet) + if (f->time_next_packet && f->time_next_packet < now) len -= min(len/2, now - f->time_next_packet); f->time_next_packet = now + len; } + out: + if (q->offload_horizon && time_next_packet <= now) + skb->tstamp = 0; + return skb; }
--
2.55.0.795.g602f6c329a-goog