[PATCH net] net/sched: sch_cake: fix autorate reconfiguration throttling

[PATCH net] net/sched: sch_cake: fix autorate reconfiguration throttling

[ooonea]

CAKE's autorate-ingress path intends to limit shaper reconfiguration to
once per 250 ms, but last_reconfig_time is only checked and never updated.
Since the field stays zero, every qualifying capacity-estimate window can
call cake_reconfigure(), causing avoidable rate churn and scheduler work
under bursty traffic.

Store the current timestamp when autorate actually reconfigures the qdisc
so the guard enforces the intended interval.

Fixes: 7298de9cd725 ("sch_cake: Add ingress mode")
Assisted-by: Codex:gpt-5.5
Signed-off-by: ooonea <ooonea@gmail.com>
---
 net/sched/sch_cake.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/sched/sch_cake.c b/net/sched/sch_cake.c
index f25f60978..dc9326702 100644
--- a/net/sched/sch_cake.c
+++ b/net/sched/sch_cake.c
@@ -1907,6 +1907,7 @@ static s32 cake_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 					ktime_add_ms(q->last_reconfig_time,
 						     250))) {
 				q->config->rate_bps = (q->avg_peak_bandwidth * 15) >> 4;
+				q->last_reconfig_time = now;
 				cake_reconfigure(sch);
 			}
 		}

base-commit: 24ef02f934eeb48830cff6b739abc3c62b1d107b
-- 
2.54.0

Re: [PATCH net] net/sched: sch_cake: fix autorate reconfiguration throttling

[Toke Høiland-Jørgensen]

ooonea <ooonea@gmail.com> writes:

> CAKE's autorate-ingress path intends to limit shaper reconfiguration to
> once per 250 ms, but last_reconfig_time is only checked and never updated.
> Since the field stays zero, every qualifying capacity-estimate window can
> call cake_reconfigure(), causing avoidable rate churn and scheduler work
> under bursty traffic.
>
> Store the current timestamp when autorate actually reconfigures the qdisc
> so the guard enforces the intended interval.
>
> Fixes: 7298de9cd725 ("sch_cake: Add ingress mode")
> Assisted-by: Codex:gpt-5.5
> Signed-off-by: ooonea <ooonea@gmail.com>

Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>