From 48da34b7a74201f15315cb1fc40bb9a7bd2b4940 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Sun, 18 Sep 2016 00:57:34 +0200 Subject: sched: add and use qdisc_skb_head helpers This change replaces sk_buff_head struct in Qdiscs with new qdisc_skb_head. Its similar to the skb_buff_head api, but does not use skb->prev pointers. Qdiscs will commonly enqueue at the tail of a list and dequeue at head. While skb_buff_head works fine for this, enqueue/dequeue needs to also adjust the prev pointer of next element. The ->prev pointer is not required for qdiscs so we can just leave it undefined and avoid one cacheline write access for en/dequeue. Suggested-by: Eric Dumazet Signed-off-by: Florian Westphal Signed-off-by: David S. Miller --- net/sched/sch_netem.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) (limited to 'net/sched/sch_netem.c') diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c index 0a964b35f8c7..9f7b380cf0a3 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -413,6 +413,16 @@ static struct sk_buff *netem_segment(struct sk_buff *skb, struct Qdisc *sch, return segs; } +static void netem_enqueue_skb_head(struct qdisc_skb_head *qh, struct sk_buff *skb) +{ + skb->next = qh->head; + + if (!qh->head) + qh->tail = skb; + qh->head = skb; + qh->qlen++; +} + /* * Insert one skb into qdisc. * Note: parent depends on return value to account for queue length. @@ -523,7 +533,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff *last; if (sch->q.qlen) - last = skb_peek_tail(&sch->q); + last = sch->q.tail; else last = netem_rb_to_skb(rb_last(&q->t_root)); if (last) { @@ -552,7 +562,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch, cb->time_to_send = psched_get_time(); q->counter = 0; - __skb_queue_head(&sch->q, skb); + netem_enqueue_skb_head(&sch->q, skb); sch->qstats.requeues++; } -- cgit v1.2.3