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Message-Id: <20241211-cake-drop-reason-v2-1-920afadf4d1b@redhat.com>
Date: Wed, 11 Dec 2024 11:17:09 +0100
From: Toke Høiland-Jørgensen <toke@...hat.com>
To: "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
Toke Høiland-Jørgensen <toke@...e.dk>,
Jamal Hadi Salim <jhs@...atatu.com>, Cong Wang <xiyou.wangcong@...il.com>,
Jiri Pirko <jiri@...nulli.us>
Cc: netdev@...r.kernel.org, cake@...ts.bufferbloat.net,
Dave Taht <dave.taht@...il.com>,
Toke Høiland-Jørgensen <toke@...hat.com>
Subject: [PATCH net-next v2] net_sched: sch_cake: Add drop reasons
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@...gle.com>
Reviewed-by: Jamal Hadi Salim <jhs@...atatu.com>
Acked-by: Dave Taht <dave.taht@...il.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
---
Changes in v2:
- Make CONGESTED and OVERLIMIT qdisc-generic instead of specific to CAKE (Jakub)
- Link to v1: https://lore.kernel.org/r/20241209-cake-drop-reason-v1-1-19205f6d1f19@redhat.com
---
include/net/dropreason-core.h | 18 ++++++++++++++++++
net/sched/sch_cake.c | 43 +++++++++++++++++++++++--------------------
2 files changed, 41 insertions(+), 20 deletions(-)
diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index c29282fabae6cdf9dd79f698b92b4b8f57156b1e..ead4170a1d0a9d3198876fabf453130bf11953be 100644
--- a/include/net/dropreason-core.h
+++ b/include/net/dropreason-core.h
@@ -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.
diff --git a/net/sched/sch_cake.c b/net/sched/sch_cake.c
index 8d8b2db4653c0c9f271f9c1953e8c61175d8f76b..deb0925f536dda69469738e45e1dbf8ed59a6820 100644
--- a/net/sched/sch_cake.c
+++ b/net/sched/sch_cake.c
@@ -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 @@ static struct sk_buff *cake_dequeue(struct Qdisc *sch)
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 @@ static struct sk_buff *cake_dequeue(struct Qdisc *sch)
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;
}
---
base-commit: 7ea2745766d776866cfbc981b21ed3cfdf50124e
change-id: 20241205-cake-drop-reason-b1661e1e7f0a
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