net_sched: accurate bytes/packets stats/rates

In commit 44b8288308ac9d (net_sched: pfifo_head_drop problem), we fixed
a problem with pfifo_head drops that incorrectly decreased
sch->bstats.bytes and sch->bstats.packets

Several qdiscs (CHOKe, SFQ, pfifo_head, ...) are able to drop a
previously enqueued packet, and bstats cannot be changed, so
bstats/rates are not accurate (over estimated)

This patch changes the qdisc_bstats updates to be done at dequeue() time
instead of enqueue() time. bstats counters no longer account for dropped
frames, and rates are more correct, since enqueue() bursts dont have
effect on dequeue() rate.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 5 deletions

diff --git a/net/sched/sch_red.c b/net/sched/sch_red.c
index a6009c5a2c97..9f98dbd32d4c 100644
--- a/net/sched/sch_red.c
+++ b/net/sched/sch_red.c
@@ -94,7 +94,6 @@ static int red_enqueue(struct sk_buff *skb, struct Qdisc* sch)
 
         ret = qdisc_enqueue(skb, child);
         if (likely(ret == NET_XMIT_SUCCESS)) {
-                qdisc_bstats_update(sch, skb);
                 sch->q.qlen++;
         } else if (net_xmit_drop_count(ret)) {
                 q->stats.pdrop++;
@@ -114,11 +113,13 @@ static struct sk_buff * red_dequeue(struct Qdisc* sch)
         struct Qdisc *child = q->qdisc;
 
         skb = child->dequeue(child);
-        if (skb)
+        if (skb) {
+                qdisc_bstats_update(sch, skb);
                 sch->q.qlen--;
-        else if (!red_is_idling(&q->parms))
-                red_start_of_idle_period(&q->parms);
-
+        } else {
+                if (!red_is_idling(&q->parms))
+                        red_start_of_idle_period(&q->parms);
+        }
         return skb;
 }