linux-kernel - [PATCH v2 net-next 04/15] net/sched: taprio: avoid calling child->ops->dequeue(child) twice

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Date:   Tue,  7 Feb 2023 15:54:29 +0200
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Jacob Keller <jacob.e.keller@...el.com>,
        Gerhard Engleder <gerhard@...leder-embedded.com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        intel-wired-lan@...ts.osuosl.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 net-next 04/15] net/sched: taprio: avoid calling child->ops->dequeue(child) twice

Simplify taprio_dequeue_from_txq() by noticing that we can goto one call
earlier than the previous skb_found label. This is possible because
we've unified the treatment of the child->ops->dequeue(child) return
call, we always try other TXQs now, instead of abandoning the root
dequeue completely if we failed in the peek() case.

Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
Reviewed-by: Kurt Kanzenbach <kurt@...utronix.de>
---
v1->v2: none

 net/sched/sch_taprio.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 272a8b7c0f9f..a3770d599a84 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -528,12 +528,8 @@ static struct sk_buff *taprio_dequeue_from_txq(struct Qdisc *sch, int txq,
 	if (unlikely(!child))
 		return NULL;
 
-	if (TXTIME_ASSIST_IS_ENABLED(q->flags)) {
-		skb = child->ops->dequeue(child);
-		if (!skb)
-			return NULL;
-		goto skb_found;
-	}
+	if (TXTIME_ASSIST_IS_ENABLED(q->flags))
+		goto skip_peek_checks;
 
 	skb = child->ops->peek(child);
 	if (!skb)
@@ -560,11 +556,11 @@ static struct sk_buff *taprio_dequeue_from_txq(struct Qdisc *sch, int txq,
 	    atomic_sub_return(len, &entry->budget) < 0)
 		return NULL;
 
+skip_peek_checks:
 	skb = child->ops->dequeue(child);
 	if (unlikely(!skb))
 		return NULL;
 
-skb_found:
 	qdisc_bstats_update(sch, skb);
 	qdisc_qstats_backlog_dec(sch, skb);
 	sch->q.qlen--;
-- 
2.34.1