netdev - [PATCH net-next] net_sched: sch_fq: tweak unlikely() hints in fq

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Message-ID: <20260203214716.880853-1-edumazet@google.com>
Date: Tue,  3 Feb 2026 21:47:16 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, Jamal Hadi Salim <jhs@...atatu.com>, Jiri Pirko <jiri@...nulli.us>, 
	netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next] net_sched: sch_fq: tweak unlikely() hints in fq_dequeue()

After 076433bd78d7 ("net_sched: sch_fq: add fast path
for mostly idle qdisc") we need to remove one unlikely()
because q->internal holds all the fast path packets.

       skb = fq_peek(&q->internal);
       if (unlikely(skb)) {
                q->internal.qlen--;

Calling INET_ECN_set_ce() is very unlikely.

These changes allow fq_dequeue_skb() to be (auto)inlined,
thus making fq_dequeue() faster.

$ scripts/bloat-o-meter -t vmlinux.0 vmlinux
add/remove: 2/2 grow/shrink: 0/1 up/down: 283/-269 (14)
Function                                     old     new   delta
INET_ECN_set_ce                                -     267    +267
__pfx_INET_ECN_set_ce                          -      16     +16
__pfx_fq_dequeue_skb                          16       -     -16
fq_dequeue_skb                               103       -    -103
fq_dequeue                                  1685    1535    -150
Total: Before=24886569, After=24886583, chg +0.00%

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/sched/sch_fq.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index 6e5f2f4f241546605f8ba37f96275446c8836eee..d0200ec8ada62e86f10d823556bedcaefb470e6c 100644
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -665,7 +665,7 @@ static struct sk_buff *fq_dequeue(struct Qdisc *sch)
 		return NULL;
 
 	skb = fq_peek(&q->internal);
-	if (unlikely(skb)) {
+	if (skb) {
 		q->internal.qlen--;
 		fq_dequeue_skb(sch, &q->internal, skb);
 		goto out;
@@ -716,7 +716,7 @@ static struct sk_buff *fq_dequeue(struct Qdisc *sch)
 		}
 		prefetch(&skb->end);
 		fq_dequeue_skb(sch, f, skb);
-		if ((s64)(now - time_next_packet - q->ce_threshold) > 0) {
+		if (unlikely((s64)(now - time_next_packet - q->ce_threshold) > 0)) {
 			INET_ECN_set_ce(skb);
 			q->stat_ce_mark++;
 		}
-- 
2.53.0.rc2.204.g2597b5adb4-goog