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net_sched: sch_cake: Add drop reasons

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Add three qdisc-specific drop reasons and use them in sch_cake:

 1) SKB_DROP_REASON_QDISC_OVERLIMIT
    Whenever the total queue limit for a qdisc instance is exceeded
    and a packet is dropped to make room.

 2) SKB_DROP_REASON_QDISC_CONGESTED
    Whenever a packet is dropped by the qdisc AQM algorithm because
    congestion is detected.

 3) SKB_DROP_REASON_CAKE_FLOOD
    Whenever a packet is dropped by the flood protection part of the
    CAKE AQM algorithm (BLUE).

Also use the existing SKB_DROP_REASON_QUEUE_PURGE in cake_clear_tin().

Reasons show up as:

perf record -a -e skb:kfree_skb sleep 1; perf script

          iperf3     665 [005]   848.656964: skb:kfree_skb: skbaddr=0xffff98168a333500 rx_sk=(nil) protocol=34525 location=__dev_queue_xmit+0x10f0 reason: QDISC_OVERLIMIT
         swapper       0 [001]   909.166055: skb:kfree_skb: skbaddr=0xffff98168280cee0 rx_sk=(nil) protocol=34525 location=cake_dequeue+0x5ef reason: QDISC_CONGESTED

Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: Dave Taht <dave.taht@gmail.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://patch.msgid.link/20241211-cake-drop-reason-v2-1-920afadf4d1b@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Toke Høiland-Jørgensen 2024-12-11 11:17:09 +01:00 • committed by Jakub Kicinski
parent 5098462fba
commit a42d71e322
2 changed files with 41 additions and 20 deletions
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18
include/net/dropreason-core.h
View file

@ -58,6 +58,9 @@
FN(TC_EGRESS) \
FN(SECURITY_HOOK) \
FN(QDISC_DROP) \
FN(QDISC_OVERLIMIT) \
FN(QDISC_CONGESTED) \
FN(CAKE_FLOOD) \
FN(FQ_BAND_LIMIT) \
FN(FQ_HORIZON_LIMIT) \
FN(FQ_FLOW_LIMIT) \
@ -314,6 +317,21 @@ enum skb_drop_reason {
* failed to enqueue to current qdisc)
*/
SKB_DROP_REASON_QDISC_DROP,
/**
* @SKB_DROP_REASON_QDISC_OVERLIMIT: dropped by qdisc when a qdisc
* instance exceeds its total buffer size limit.
*/
SKB_DROP_REASON_QDISC_OVERLIMIT,
/**
* @SKB_DROP_REASON_QDISC_CONGESTED: dropped by a qdisc AQM algorithm
* due to congestion.
*/
SKB_DROP_REASON_QDISC_CONGESTED,
/**
* @SKB_DROP_REASON_CAKE_FLOOD: dropped by the flood protection part of
* CAKE qdisc AQM algorithm (BLUE).
*/
SKB_DROP_REASON_CAKE_FLOOD,
/**
* @SKB_DROP_REASON_FQ_BAND_LIMIT: dropped by fq qdisc when per band
* limit is reached.

43
net/sched/sch_cake.c
View file

@ -484,13 +484,14 @@ static bool cobalt_queue_empty(struct cobalt_vars *vars,
/* Call this with a freshly dequeued packet for possible congestion marking.
* Returns true as an instruction to drop the packet, false for delivery.
*/
static bool cobalt_should_drop(struct cobalt_vars *vars,
struct cobalt_params *p,
ktime_t now,
struct sk_buff *skb,
u32 bulk_flows)
static enum skb_drop_reason cobalt_should_drop(struct cobalt_vars *vars,
struct cobalt_params *p,
ktime_t now,
struct sk_buff *skb,
u32 bulk_flows)
{
bool next_due, over_target, drop = false;
enum skb_drop_reason reason = SKB_NOT_DROPPED_YET;
bool next_due, over_target;
ktime_t schedule;
u64 sojourn;
@ -533,7 +534,8 @@ static bool cobalt_should_drop(struct cobalt_vars *vars,
if (next_due && vars->dropping) {
/* Use ECN mark if possible, otherwise drop */
drop = !(vars->ecn_marked = INET_ECN_set_ce(skb));
if (!(vars->ecn_marked = INET_ECN_set_ce(skb)))
reason = SKB_DROP_REASON_QDISC_CONGESTED;
vars->count++;
if (!vars->count)
@ -556,16 +558,17 @@ static bool cobalt_should_drop(struct cobalt_vars *vars,
}
/* Simple BLUE implementation. Lack of ECN is deliberate. */
if (vars->p_drop)
drop |= (get_random_u32() < vars->p_drop);
if (vars->p_drop && reason == SKB_NOT_DROPPED_YET &&
get_random_u32() < vars->p_drop)
reason = SKB_DROP_REASON_CAKE_FLOOD;
/* Overload the drop_next field as an activity timeout */
if (!vars->count)
vars->drop_next = ktime_add_ns(now, p->interval);
else if (ktime_to_ns(schedule) > 0 && !drop)
else if (ktime_to_ns(schedule) > 0 && reason == SKB_NOT_DROPPED_YET)
vars->drop_next = now;
return drop;
return reason;
}
static bool cake_update_flowkeys(struct flow_keys *keys,
@ -1528,12 +1531,11 @@ static unsigned int cake_drop(struct Qdisc *sch, struct sk_buff **to_free)
flow->dropped++;
b->tin_dropped++;
sch->qstats.drops++;
if (q->rate_flags & CAKE_FLAG_INGRESS)
cake_advance_shaper(q, b, skb, now, true);
__qdisc_drop(skb, to_free);
qdisc_drop_reason(skb, sch, to_free, SKB_DROP_REASON_QDISC_OVERLIMIT);
sch->q.qlen--;
qdisc_tree_reduce_backlog(sch, 1, len);
@ -1926,7 +1928,7 @@ static void cake_clear_tin(struct Qdisc *sch, u16 tin)
q->cur_tin = tin;
for (q->cur_flow = 0; q->cur_flow < CAKE_QUEUES; q->cur_flow++)
while (!!(skb = cake_dequeue_one(sch)))
kfree_skb(skb);
kfree_skb_reason(skb, SKB_DROP_REASON_QUEUE_PURGE);
}
static struct sk_buff *cake_dequeue(struct Qdisc *sch)
@ -1934,6 +1936,7 @@ static struct sk_buff *cake_dequeue(struct Qdisc *sch)
struct cake_sched_data *q = qdisc_priv(sch);
struct cake_tin_data *b = &q->tins[q->cur_tin];
struct cake_host *srchost, *dsthost;
enum skb_drop_reason reason;
ktime_t now = ktime_get();
struct cake_flow *flow;
struct list_head *head;
@ -2143,12 +2146,12 @@ retry:
goto begin;
}
reason = cobalt_should_drop(&flow->cvars, &b->cparams, now, skb,
(b->bulk_flow_count *
!!(q->rate_flags &
CAKE_FLAG_INGRESS)));
/* Last packet in queue may be marked, shouldn't be dropped */
if (!cobalt_should_drop(&flow->cvars, &b->cparams, now, skb,
(b->bulk_flow_count *
!!(q->rate_flags &
CAKE_FLAG_INGRESS))) ||
!flow->head)
if (reason == SKB_NOT_DROPPED_YET || !flow->head)
break;
/* drop this packet, get another one */
@ -2162,7 +2165,7 @@ retry:
b->tin_dropped++;
qdisc_tree_reduce_backlog(sch, 1, qdisc_pkt_len(skb));
qdisc_qstats_drop(sch);
kfree_skb(skb);
kfree_skb_reason(skb, reason);
if (q->rate_flags & CAKE_FLAG_INGRESS)
goto retry;
}