Re: [PATCH net-next 3/4] net_sched: sch_fq: add fast path for mostly idle qdisc

Re: [PATCH net-next 3/4] net_sched: sch_fq: add fast path for mostly idle qdisc

[kernel test robot]

:::::: 
:::::: Manual check reason: "low confidence static check warning: net/sched/sch_fq.c:550:1: sparse: sparse: unused label 'queue'"
:::::: 

BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
In-Reply-To: <20230920125418.3675569-4-edumazet@google.com>
References: <20230920125418.3675569-4-edumazet@google.com>
TO: Eric Dumazet <edumazet@google.com>
TO: "David S . Miller" <davem@davemloft.net>
TO: Jakub Kicinski <kuba@kernel.org>
TO: Paolo Abeni <pabeni@redhat.com>
CC: Willem de Bruijn <willemb@google.com>
CC: Jamal Hadi Salim <jhs@mojatatu.com>
CC: Cong Wang <xiyou.wangcong@gmail.com>
CC: Jiri Pirko <jiri@resnulli.us>
CC: netdev@vger.kernel.org
CC: eric.dumazet@gmail.com
CC: Eric Dumazet <edumazet@google.com>

Hi Eric,

kernel test robot noticed the following build warnings:

[auto build test WARNING on net-next/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Eric-Dumazet/net_sched-sch_fq-struct-sched_data-reorg/20230920-205744
base:   net-next/main
patch link:    https://lore.kernel.org/r/20230920125418.3675569-4-edumazet%40google.com
patch subject: [PATCH net-next 3/4] net_sched: sch_fq: add fast path for mostly idle qdisc
:::::: branch date: 5 days ago
:::::: commit date: 5 days ago
config: x86_64-randconfig-123-20230925 (https://download.01.org/0day-ci/archive/20230925/202309252000.LAvn3XwF-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20230925/202309252000.LAvn3XwF-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/r/202309252000.LAvn3XwF-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> net/sched/sch_fq.c:550:1: sparse: sparse: unused label 'queue'

vim +/queue +550 net/sched/sch_fq.c

39d010504e6b44 Eric Dumazet 2020-05-01  505  
b2377bef637585 Eric Dumazet 2023-09-20  506  
520ac30f45519b Eric Dumazet 2016-06-21  507  static int fq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
520ac30f45519b Eric Dumazet 2016-06-21  508  		      struct sk_buff **to_free)
afe4fd062416b1 Eric Dumazet 2013-08-29  509  {
afe4fd062416b1 Eric Dumazet 2013-08-29  510  	struct fq_sched_data *q = qdisc_priv(sch);
afe4fd062416b1 Eric Dumazet 2013-08-29  511  	struct fq_flow *f;
afe4fd062416b1 Eric Dumazet 2013-08-29  512  
afe4fd062416b1 Eric Dumazet 2013-08-29  513  	if (unlikely(sch->q.qlen >= sch->limit))
520ac30f45519b Eric Dumazet 2016-06-21  514  		return qdisc_drop(skb, sch, to_free);
afe4fd062416b1 Eric Dumazet 2013-08-29  515  
b2377bef637585 Eric Dumazet 2023-09-20  516  	q->ktime_cache = ktime_get_ns();
39d010504e6b44 Eric Dumazet 2020-05-01  517  	if (!skb->tstamp) {
b2377bef637585 Eric Dumazet 2023-09-20  518  		fq_skb_cb(skb)->time_to_send = q->ktime_cache;
39d010504e6b44 Eric Dumazet 2020-05-01  519  	} else {
b2377bef637585 Eric Dumazet 2023-09-20  520  		/* Check if packet timestamp is too far in the future. */
39d010504e6b44 Eric Dumazet 2020-05-01  521  		if (fq_packet_beyond_horizon(skb, q)) {
39d010504e6b44 Eric Dumazet 2020-05-01  522  			if (q->horizon_drop) {
39d010504e6b44 Eric Dumazet 2020-05-01  523  					q->stat_horizon_drops++;
39d010504e6b44 Eric Dumazet 2020-05-01  524  					return qdisc_drop(skb, sch, to_free);
39d010504e6b44 Eric Dumazet 2020-05-01  525  			}
39d010504e6b44 Eric Dumazet 2020-05-01  526  			q->stat_horizon_caps++;
39d010504e6b44 Eric Dumazet 2020-05-01  527  			skb->tstamp = q->ktime_cache + q->horizon;
39d010504e6b44 Eric Dumazet 2020-05-01  528  		}
39d010504e6b44 Eric Dumazet 2020-05-01  529  		fq_skb_cb(skb)->time_to_send = skb->tstamp;
39d010504e6b44 Eric Dumazet 2020-05-01  530  	}
39d010504e6b44 Eric Dumazet 2020-05-01  531  
b2377bef637585 Eric Dumazet 2023-09-20  532  	f = fq_classify(sch, skb);
afe4fd062416b1 Eric Dumazet 2013-08-29  533  	if (unlikely(f->qlen >= q->flow_plimit && f != &q->internal)) {
afe4fd062416b1 Eric Dumazet 2013-08-29  534  		q->stat_flows_plimit++;
520ac30f45519b Eric Dumazet 2016-06-21  535  		return qdisc_drop(skb, sch, to_free);
afe4fd062416b1 Eric Dumazet 2013-08-29  536  	}
afe4fd062416b1 Eric Dumazet 2013-08-29  537  
afe4fd062416b1 Eric Dumazet 2013-08-29  538  	if (fq_flow_is_detached(f)) {
afe4fd062416b1 Eric Dumazet 2013-08-29  539  		fq_flow_add_tail(&q->new_flows, f);
f52ed89971adbe Eric Dumazet 2013-11-15  540  		if (time_after(jiffies, f->age + q->flow_refill_delay))
f52ed89971adbe Eric Dumazet 2013-11-15  541  			f->credit = max_t(u32, f->credit, q->quantum);
afe4fd062416b1 Eric Dumazet 2013-08-29  542  	}
f52ed89971adbe Eric Dumazet 2013-11-15  543  
afe4fd062416b1 Eric Dumazet 2013-08-29  544  	if (unlikely(f == &q->internal)) {
afe4fd062416b1 Eric Dumazet 2013-08-29  545  		q->stat_internal_packets++;
b2377bef637585 Eric Dumazet 2023-09-20  546  	} else {
b2377bef637585 Eric Dumazet 2023-09-20  547  		if (f->qlen == 0)
b2377bef637585 Eric Dumazet 2023-09-20  548  			q->inactive_flows--;
afe4fd062416b1 Eric Dumazet 2013-08-29  549  	}
b2377bef637585 Eric Dumazet 2023-09-20 @550  queue:
b2377bef637585 Eric Dumazet 2023-09-20  551  	f->qlen++;
b2377bef637585 Eric Dumazet 2023-09-20  552  	/* Note: this overwrites f->age */
b2377bef637585 Eric Dumazet 2023-09-20  553  	flow_queue_add(f, skb);
b2377bef637585 Eric Dumazet 2023-09-20  554  
b2377bef637585 Eric Dumazet 2023-09-20  555  	qdisc_qstats_backlog_inc(sch, skb);
afe4fd062416b1 Eric Dumazet 2013-08-29  556  	sch->q.qlen++;
afe4fd062416b1 Eric Dumazet 2013-08-29  557  
afe4fd062416b1 Eric Dumazet 2013-08-29  558  	return NET_XMIT_SUCCESS;
afe4fd062416b1 Eric Dumazet 2013-08-29  559  }
afe4fd062416b1 Eric Dumazet 2013-08-29  560  

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

[PATCH net-next 0/4] net_sched: sch_fq: round of improvements

[Eric Dumazet]

For FQ tenth anniversary, it was time for making it faster.

The FQ part (as in Fair Queue) is rather expensive, because
we have to classify packets and store them in a per-flow structure,
and add this per-flow structure in a hash table.

Most fq qdisc are almost idle. Trying to share NIC bandwidth has
no benefits, thus the qdisc could behave like a FIFO.

Eric Dumazet (4):
  net_sched: sch_fq: struct sched_data reorg
  net_sched: sch_fq: change how @inactive is tracked
  net_sched: sch_fq: add fast path for mostly idle qdisc
  net_sched: sch_fq: always garbage collect

 include/uapi/linux/pkt_sched.h |   1 +
 net/sched/sch_fq.c             | 127 ++++++++++++++++++++++++---------
 2 files changed, 96 insertions(+), 32 deletions(-)

-- 
2.42.0.459.ge4e396fd5e-goog

[PATCH net-next 3/4] net_sched: sch_fq: add fast path for mostly idle qdisc

[Eric Dumazet]

TCQ_F_CAN_BYPASS can be used by few qdiscs.

Idea is that if we queue a packet to an empty qdisc,
following dequeue() would pick it immediately.

FQ can not use the generic TCQ_F_CAN_BYPASS code,
because some additional checks need to be performed.

This patch adds a similar fast path to FQ.

Most of the time, qdisc is not throttled,
and many packets can avoid bringing/touching
at least four cache lines, and consuming 128bytes
of memory to store the state of a flow.

After this patch, netperf can send UDP packets about 13 % faster,
and pktgen goes 30 % faster (when FQ is in the way), on a fast NIC.

TCP traffic is also improved, thanks to a reduction of cache line misses.

tc -s -d qd sh dev eth1
...
qdisc fq 8004: parent 1:2 limit 10000p flow_limit 100p buckets 1024
   orphan_mask 1023 quantum 3028b initial_quantum 15140b low_rate_threshold 550Kbit
   refill_delay 40ms timer_slack 10us horizon 10s horizon_drop
 Sent 5646784384 bytes 1985161 pkt (dropped 0, overlimits 0 requeues 0)
 backlog 0b 0p requeues 0
  flows 122 (inactive 122 throttled 0)
  gc 0 highprio 0 fastpath 659990 throttled 27762 latency 8.57us

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/uapi/linux/pkt_sched.h |   1 +
 net/sched/sch_fq.c             | 107 +++++++++++++++++++++++++--------
 2 files changed, 82 insertions(+), 26 deletions(-)

diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
index 3f85ae5780563cdfb42fdb3a107ca2489d0830a4..579f641846b87da05e5d4b09c1072c90220ca601 100644
--- a/include/uapi/linux/pkt_sched.h
+++ b/include/uapi/linux/pkt_sched.h
@@ -962,6 +962,7 @@ struct tc_fq_qd_stats {
 	__u64	ce_mark;		/* packets above ce_threshold */
 	__u64	horizon_drops;
 	__u64	horizon_caps;
+	__u64	fastpath_packets;
 };
 
 /* Heavy-Hitter Filter */
diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index 4af43a401dbb4111d5cfaddb4b83fc5c7b63b83d..ea510003bc385148397a690c5afd9387fba9796c 100644
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -2,7 +2,7 @@
 /*
  * net/sched/sch_fq.c Fair Queue Packet Scheduler (per flow pacing)
  *
- *  Copyright (C) 2013-2015 Eric Dumazet <edumazet@google.com>
+ *  Copyright (C) 2013-2023 Eric Dumazet <edumazet@google.com>
  *
  *  Meant to be mostly used for locally generated traffic :
  *  Fast classification depends on skb->sk being set before reaching us.
@@ -73,7 +73,13 @@ struct fq_flow {
 		struct sk_buff *tail;	/* last skb in the list */
 		unsigned long  age;	/* (jiffies | 1UL) when flow was emptied, for gc */
 	};
-	struct rb_node	fq_node;	/* anchor in fq_root[] trees */
+	union {
+		struct rb_node	fq_node;	/* anchor in fq_root[] trees */
+		/* Following field is only used for q->internal,
+		 * because q->internal is not hashed in fq_root[]
+		 */
+		u64		stat_fastpath_packets;
+	};
 	struct sock	*sk;
 	u32		socket_hash;	/* sk_hash */
 	int		qlen;		/* number of packets in flow queue */
@@ -266,8 +272,56 @@ static void fq_gc(struct fq_sched_data *q,
 	kmem_cache_free_bulk(fq_flow_cachep, fcnt, tofree);
 }
 
-static struct fq_flow *fq_classify(struct sk_buff *skb, struct fq_sched_data *q)
+/* Fast path can be used if :
+ * 1) Packet tstamp is in the past.
+ * 2) FQ qlen == 0   OR
+ *   (no flow is currently elligible for transmit,
+ *    AND fast path queue has less than 8 packets)
+ * 3) No SO_MAX_PACING_RATE on the socket (if any).
+ * 4) No @maxrate attribute on this qdisc,
+ *
+ * FQ can not use generic TCQ_F_CAN_BYPASS infrastructure.
+ */
+static bool fq_fastpath_check(struct Qdisc *sch, struct sk_buff *skb)
 {
+	struct fq_sched_data *q = qdisc_priv(sch);
+	const struct sock *sk;
+
+	if (fq_skb_cb(skb)->time_to_send > q->ktime_cache)
+		return false;
+
+	if (sch->q.qlen != 0) {
+		/* Even if some packets are stored in this qdisc,
+		 * we can still enable fast path if all of them are
+		 * scheduled in the future (ie no flows are elligible)
+		 * or in the fast path queue.
+		 */
+		if (q->flows != q->inactive_flows + q->throttled_flows)
+			return false;
+
+		/* Do not allow fast path queue to explode, we want Fair Queue mode
+		 * under pressure.
+		 */
+		if (q->internal.qlen >= 8)
+			return false;
+	}
+
+	sk = skb->sk;
+	if (sk && sk_fullsock(sk) && !sk_is_tcp(sk) &&
+	    sk->sk_max_pacing_rate != ~0UL)
+		return false;
+
+	if (q->flow_max_rate != ~0UL)
+		return false;
+
+	q->internal.stat_fastpath_packets++;
+
+	return true;
+}
+
+static struct fq_flow *fq_classify(struct Qdisc *sch, struct sk_buff *skb)
+{
+	struct fq_sched_data *q = qdisc_priv(sch);
 	struct rb_node **p, *parent;
 	struct sock *sk = skb->sk;
 	struct rb_root *root;
@@ -307,6 +361,9 @@ static struct fq_flow *fq_classify(struct sk_buff *skb, struct fq_sched_data *q)
 		sk = (struct sock *)((hash << 1) | 1UL);
 	}
 
+	if (fq_fastpath_check(sch, skb))
+		return &q->internal;
+
 	root = &q->fq_root[hash_ptr(sk, q->fq_trees_log)];
 
 	if (q->flows >= (2U << q->fq_trees_log) &&
@@ -402,12 +459,8 @@ static void fq_erase_head(struct Qdisc *sch, struct fq_flow *flow,
 static void fq_dequeue_skb(struct Qdisc *sch, struct fq_flow *flow,
 			   struct sk_buff *skb)
 {
-	struct fq_sched_data *q = qdisc_priv(sch);
-
 	fq_erase_head(sch, flow, skb);
 	skb_mark_not_on_list(skb);
-	if (--flow->qlen == 0)
-		q->inactive_flows++;
 	qdisc_qstats_backlog_dec(sch, skb);
 	sch->q.qlen--;
 }
@@ -450,6 +503,7 @@ static bool fq_packet_beyond_horizon(const struct sk_buff *skb,
 	return unlikely((s64)skb->tstamp > (s64)(q->ktime_cache + q->horizon));
 }
 
+
 static int fq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 		      struct sk_buff **to_free)
 {
@@ -459,49 +513,46 @@ static int fq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 	if (unlikely(sch->q.qlen >= sch->limit))
 		return qdisc_drop(skb, sch, to_free);
 
+	q->ktime_cache = ktime_get_ns();
 	if (!skb->tstamp) {
-		fq_skb_cb(skb)->time_to_send = q->ktime_cache = ktime_get_ns();
+		fq_skb_cb(skb)->time_to_send = q->ktime_cache;
 	} else {
-		/* Check if packet timestamp is too far in the future.
-		 * Try first if our cached value, to avoid ktime_get_ns()
-		 * cost in most cases.
-		 */
+		/* Check if packet timestamp is too far in the future. */
 		if (fq_packet_beyond_horizon(skb, q)) {
-			/* Refresh our cache and check another time */
-			q->ktime_cache = ktime_get_ns();
-			if (fq_packet_beyond_horizon(skb, q)) {
-				if (q->horizon_drop) {
+			if (q->horizon_drop) {
 					q->stat_horizon_drops++;
 					return qdisc_drop(skb, sch, to_free);
-				}
-				q->stat_horizon_caps++;
-				skb->tstamp = q->ktime_cache + q->horizon;
 			}
+			q->stat_horizon_caps++;
+			skb->tstamp = q->ktime_cache + q->horizon;
 		}
 		fq_skb_cb(skb)->time_to_send = skb->tstamp;
 	}
 
-	f = fq_classify(skb, q);
+	f = fq_classify(sch, skb);
 	if (unlikely(f->qlen >= q->flow_plimit && f != &q->internal)) {
 		q->stat_flows_plimit++;
 		return qdisc_drop(skb, sch, to_free);
 	}
 
-	if (f->qlen++ == 0)
-		q->inactive_flows--;
-	qdisc_qstats_backlog_inc(sch, skb);
 	if (fq_flow_is_detached(f)) {
 		fq_flow_add_tail(&q->new_flows, f);
 		if (time_after(jiffies, f->age + q->flow_refill_delay))
 			f->credit = max_t(u32, f->credit, q->quantum);
 	}
 
-	/* Note: this overwrites f->age */
-	flow_queue_add(f, skb);
-
 	if (unlikely(f == &q->internal)) {
 		q->stat_internal_packets++;
+	} else {
+		if (f->qlen == 0)
+			q->inactive_flows--;
 	}
+queue:
+	f->qlen++;
+	/* Note: this overwrites f->age */
+	flow_queue_add(f, skb);
+
+	qdisc_qstats_backlog_inc(sch, skb);
 	sch->q.qlen++;
 
 	return NET_XMIT_SUCCESS;
@@ -549,6 +600,7 @@ static struct sk_buff *fq_dequeue(struct Qdisc *sch)
 
 	skb = fq_peek(&q->internal);
 	if (unlikely(skb)) {
+		q->internal.qlen--;
 		fq_dequeue_skb(sch, &q->internal, skb);
 		goto out;
 	}
@@ -592,6 +644,8 @@ static struct sk_buff *fq_dequeue(struct Qdisc *sch)
 			INET_ECN_set_ce(skb);
 			q->stat_ce_mark++;
 		}
+		if (--f->qlen == 0)
+			q->inactive_flows++;
 		fq_dequeue_skb(sch, f, skb);
 	} else {
 		head->first = f->next;
@@ -1024,6 +1078,7 @@ static int fq_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
 
 	st.gc_flows		  = q->stat_gc_flows;
 	st.highprio_packets	  = q->stat_internal_packets;
+	st.fastpath_packets	  = q->internal.stat_fastpath_packets;
 	st.tcp_retrans		  = 0;
 	st.throttled		  = q->stat_throttled;
 	st.flows_plimit		  = q->stat_flows_plimit;
-- 
2.42.0.459.ge4e396fd5e-goog

Re: [PATCH net-next 3/4] net_sched: sch_fq: add fast path for mostly idle qdisc

[kernel test robot]

Hi Eric,

kernel test robot noticed the following build warnings:

[auto build test WARNING on net-next/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Eric-Dumazet/net_sched-sch_fq-struct-sched_data-reorg/20230920-205744
base:   net-next/main
patch link:    https://lore.kernel.org/r/20230920125418.3675569-4-edumazet%40google.com
patch subject: [PATCH net-next 3/4] net_sched: sch_fq: add fast path for mostly idle qdisc
config: m68k-allyesconfig (https://download.01.org/0day-ci/archive/20230920/202309202157.1I3oSZoS-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20230920/202309202157.1I3oSZoS-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202309202157.1I3oSZoS-lkp@intel.com/

All warnings (new ones prefixed by >>):

   net/sched/sch_fq.c: In function 'fq_enqueue':
>> net/sched/sch_fq.c:550:1: warning: label 'queue' defined but not used [-Wunused-label]
     550 | queue:
         | ^~~~~


vim +/queue +550 net/sched/sch_fq.c

   505	
   506	
   507	static int fq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
   508			      struct sk_buff **to_free)
   509	{
   510		struct fq_sched_data *q = qdisc_priv(sch);
   511		struct fq_flow *f;
   512	
   513		if (unlikely(sch->q.qlen >= sch->limit))
   514			return qdisc_drop(skb, sch, to_free);
   515	
   516		q->ktime_cache = ktime_get_ns();
   517		if (!skb->tstamp) {
   518			fq_skb_cb(skb)->time_to_send = q->ktime_cache;
   519		} else {
   520			/* Check if packet timestamp is too far in the future. */
   521			if (fq_packet_beyond_horizon(skb, q)) {
   522				if (q->horizon_drop) {
   523						q->stat_horizon_drops++;
   524						return qdisc_drop(skb, sch, to_free);
   525				}
   526				q->stat_horizon_caps++;
   527				skb->tstamp = q->ktime_cache + q->horizon;
   528			}
   529			fq_skb_cb(skb)->time_to_send = skb->tstamp;
   530		}
   531	
   532		f = fq_classify(sch, skb);
   533		if (unlikely(f->qlen >= q->flow_plimit && f != &q->internal)) {
   534			q->stat_flows_plimit++;
   535			return qdisc_drop(skb, sch, to_free);
   536		}
   537	
   538		if (fq_flow_is_detached(f)) {
   539			fq_flow_add_tail(&q->new_flows, f);
   540			if (time_after(jiffies, f->age + q->flow_refill_delay))
   541				f->credit = max_t(u32, f->credit, q->quantum);
   542		}
   543	
   544		if (unlikely(f == &q->internal)) {
   545			q->stat_internal_packets++;
   546		} else {
   547			if (f->qlen == 0)
   548				q->inactive_flows--;
   549		}
 > 550	queue:
   551		f->qlen++;
   552		/* Note: this overwrites f->age */
   553		flow_queue_add(f, skb);
   554	
   555		qdisc_qstats_backlog_inc(sch, skb);
   556		sch->q.qlen++;
   557	
   558		return NET_XMIT_SUCCESS;
   559	}
   560	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH net-next 3/4] net_sched: sch_fq: add fast path for mostly idle qdisc

[kernel test robot]

Hi Eric,

kernel test robot noticed the following build warnings:

[auto build test WARNING on net-next/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Eric-Dumazet/net_sched-sch_fq-struct-sched_data-reorg/20230920-205744
base:   net-next/main
patch link:    https://lore.kernel.org/r/20230920125418.3675569-4-edumazet%40google.com
patch subject: [PATCH net-next 3/4] net_sched: sch_fq: add fast path for mostly idle qdisc
config: x86_64-rhel-8.3-rust (https://download.01.org/0day-ci/archive/20230925/202309251006.HEmH6uZd-lkp@intel.com/config)
compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20230925/202309251006.HEmH6uZd-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202309251006.HEmH6uZd-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> net/sched/sch_fq.c:550:1: warning: unused label 'queue' [-Wunused-label]
   queue:
   ^~~~~~
   1 warning generated.


vim +/queue +550 net/sched/sch_fq.c

   505	
   506	
   507	static int fq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
   508			      struct sk_buff **to_free)
   509	{
   510		struct fq_sched_data *q = qdisc_priv(sch);
   511		struct fq_flow *f;
   512	
   513		if (unlikely(sch->q.qlen >= sch->limit))
   514			return qdisc_drop(skb, sch, to_free);
   515	
   516		q->ktime_cache = ktime_get_ns();
   517		if (!skb->tstamp) {
   518			fq_skb_cb(skb)->time_to_send = q->ktime_cache;
   519		} else {
   520			/* Check if packet timestamp is too far in the future. */
   521			if (fq_packet_beyond_horizon(skb, q)) {
   522				if (q->horizon_drop) {
   523						q->stat_horizon_drops++;
   524						return qdisc_drop(skb, sch, to_free);
   525				}
   526				q->stat_horizon_caps++;
   527				skb->tstamp = q->ktime_cache + q->horizon;
   528			}
   529			fq_skb_cb(skb)->time_to_send = skb->tstamp;
   530		}
   531	
   532		f = fq_classify(sch, skb);
   533		if (unlikely(f->qlen >= q->flow_plimit && f != &q->internal)) {
   534			q->stat_flows_plimit++;
   535			return qdisc_drop(skb, sch, to_free);
   536		}
   537	
   538		if (fq_flow_is_detached(f)) {
   539			fq_flow_add_tail(&q->new_flows, f);
   540			if (time_after(jiffies, f->age + q->flow_refill_delay))
   541				f->credit = max_t(u32, f->credit, q->quantum);
   542		}
   543	
   544		if (unlikely(f == &q->internal)) {
   545			q->stat_internal_packets++;
   546		} else {
   547			if (f->qlen == 0)
   548				q->inactive_flows--;
   549		}
 > 550	queue:
   551		f->qlen++;
   552		/* Note: this overwrites f->age */
   553		flow_queue_add(f, skb);
   554	
   555		qdisc_qstats_backlog_inc(sch, skb);
   556		sch->q.qlen++;
   557	
   558		return NET_XMIT_SUCCESS;
   559	}
   560	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki