[NETEM]: Optimize tfifo

In most cases, the next packet will be sent after the
last one. So optimize that case.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 4ac6df0a5b3551be6e373a40d47835092fc95038..7e9e658d4d93dd6c0d1270c6b25222e8f00234ef 100644 (file)
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -479,22 +479,28 @@ static int netem_change(struct Qdisc *sch, struct rtattr *opt)
  */
 struct fifo_sched_data {
        u32 limit;
+       psched_time_t oldest;
 };
 
 static int tfifo_enqueue(struct sk_buff *nskb, struct Qdisc *sch)
 {
        struct fifo_sched_data *q = qdisc_priv(sch);
        struct sk_buff_head *list = &sch->q;
-       const struct netem_skb_cb *ncb
-               = (const struct netem_skb_cb *)nskb->cb;
+       psched_time_t tnext = ((struct netem_skb_cb *)nskb->cb)->time_to_send;
        struct sk_buff *skb;
 
        if (likely(skb_queue_len(list) < q->limit)) {
+               /* Optimize for add at tail */
+               if (likely(skb_queue_empty(list) || !PSCHED_TLESS(tnext, q->oldest))) {
+                       q->oldest = tnext;
+                       return qdisc_enqueue_tail(nskb, sch);
+               }
+
                skb_queue_reverse_walk(list, skb) {
                        const struct netem_skb_cb *cb
                                = (const struct netem_skb_cb *)skb->cb;
 
-                       if (!PSCHED_TLESS(ncb->time_to_send, cb->time_to_send))
+                       if (!PSCHED_TLESS(tnext, cb->time_to_send))
                                break;
                }
 
@@ -507,7 +513,7 @@ static int tfifo_enqueue(struct sk_buff *nskb, struct Qdisc *sch)
                return NET_XMIT_SUCCESS;
        }
 
-       return qdisc_drop(nskb, sch);
+       return qdisc_reshape_fail(nskb, sch);
 }
 
 static int tfifo_init(struct Qdisc *sch, struct rtattr *opt)
@@ -523,6 +529,7 @@ static int tfifo_init(struct Qdisc *sch, struct rtattr *opt)
        } else
                q->limit = max_t(u32, sch->dev->tx_queue_len, 1);
 
+       PSCHED_SET_PASTPERFECT(q->oldest);
        return 0;
 }