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net: sch_fq: update flow delivery time on earlier EDT packet

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When inserting an EDT packet with time before flow->time_next_packet,
update the flow and possibly queue next delivery time.

Reinsert the flow into the q->delayed rb-tree to position correctly
and to have fq_check_throttled set wake-up at the right next time.

Factor RB tree insertion out fq_flow_set_throttled to avoid open
coding twice.

EDT packets do not take precedence over queue rate limit. Skip this
new step if a queue limit is set. EDT packets do take precedence over
per-socket rate limits, as can be seen from fq_dequeue reading
sk_pacing_rate if !skb->tstamp.

With this change the so_txtime selftest sends packets in the expected
order.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20260526134109.2624493-1-willemdebruijn.kernel@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Willem de Bruijn 2026-05-26 09:40:37 -04:00 committed by Jakub Kicinski
parent 56edbedb74
commit fabcf8cad6
2 changed files with 31 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
net/sched/sch_fq.c
View File

@ -217,7 +217,7 @@ static void fq_flow_unset_throttled(struct fq_sched_data *q, struct fq_flow *f)
fq_flow_add_tail(q, f, OLD_FLOW);
}
static void fq_flow_set_throttled(struct fq_sched_data *q, struct fq_flow *f)
static void fq_flow_rb_insert(struct fq_sched_data *q, struct fq_flow *f)
{
struct rb_node **p = &q->delayed.rb_node, *parent = NULL;
@ -233,14 +233,18 @@ static void fq_flow_set_throttled(struct fq_sched_data *q, struct fq_flow *f)
}
rb_link_node(&f->rate_node, parent, p);
rb_insert_color(&f->rate_node, &q->delayed);
q->throttled_flows++;
q->stat_throttled++;
f->next = &throttled;
if (q->time_next_delayed_flow > f->time_next_packet)
q->time_next_delayed_flow = f->time_next_packet;
}
static void fq_flow_set_throttled(struct fq_sched_data *q, struct fq_flow *f)
{
fq_flow_rb_insert(q, f);
q->throttled_flows++;
q->stat_throttled++;
f->next = &throttled;
}
static struct kmem_cache *fq_flow_cachep __read_mostly;
@ -539,6 +543,24 @@ static bool fq_packet_beyond_horizon(const struct sk_buff *skb,
return unlikely((s64)skb->tstamp > (s64)(now + q->horizon));
}
static void fq_flow_adjust_timer(struct fq_sched_data *q, struct fq_flow *flow,
u64 time_to_send, u64 now)
{
if (time_to_send <= now) {
fq_flow_unset_throttled(q, flow);
if (q->time_next_delayed_flow == flow->time_next_packet) {
struct rb_node *p = rb_first(&q->delayed);
q->time_next_delayed_flow = p ? rb_entry(p, struct fq_flow, rate_node)->time_next_packet : ~0ULL;
}
flow->time_next_packet = time_to_send;
} else {
rb_erase(&flow->rate_node, &q->delayed);
flow->time_next_packet = time_to_send;
fq_flow_rb_insert(q, flow);
}
}
static int fq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
struct sk_buff **to_free)
{
@ -596,6 +618,10 @@ static int fq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
/* Note: this overwrites f->age */
flow_queue_add(f, skb);
if (fq_skb_cb(skb)->time_to_send < f->time_next_packet && skb->tstamp &&
fq_flow_is_throttled(f) && q->flow_max_rate == ~0UL)
fq_flow_adjust_timer(q, f, fq_skb_cb(skb)->time_to_send, now);
qdisc_qstats_backlog_inc(sch, skb);
qdisc_qlen_inc(sch);

2
tools/testing/selftests/drivers/net/so_txtime.py
View File

@ -53,7 +53,7 @@ def _test_variants_mono():
["zero_delay", "a,0", "a,0"],
["one_pkt", "a,10", "a,10"],
["in_order", "a,10,b,20", "a,10,b,20"],
["reverse_order", "a,20,b,10", "b,20,a,20"],
["reverse_order", "a,20,b,10", "b,10,a,20"],
]:
name = f"v{ipver}_{testcase[0]}"
yield KsftNamedVariant(name, ipver, testcase[1], testcase[2])