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, 5 insertions, 3 deletions

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index e9eee99d8b1f..160a407c1963 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -445,7 +445,6 @@ static inline int __qdisc_enqueue_tail(struct sk_buff *skb, struct Qdisc *sch,
 {
         __skb_queue_tail(list, skb);
         sch->qstats.backlog += qdisc_pkt_len(skb);
-        qdisc_bstats_update(sch, skb);
 
         return NET_XMIT_SUCCESS;
 }
@@ -460,8 +459,10 @@ static inline struct sk_buff *__qdisc_dequeue_head(struct Qdisc *sch,
 {
         struct sk_buff *skb = __skb_dequeue(list);
 
-        if (likely(skb != NULL))
+        if (likely(skb != NULL)) {
                 sch->qstats.backlog -= qdisc_pkt_len(skb);
+                qdisc_bstats_update(sch, skb);
+        }
 
         return skb;
 }
@@ -474,10 +475,11 @@ static inline struct sk_buff *qdisc_dequeue_head(struct Qdisc *sch)
 static inline unsigned int __qdisc_queue_drop_head(struct Qdisc *sch,
                                               struct sk_buff_head *list)
 {
-        struct sk_buff *skb = __qdisc_dequeue_head(sch, list);
+        struct sk_buff *skb = __skb_dequeue(list);
 
         if (likely(skb != NULL)) {
                 unsigned int len = qdisc_pkt_len(skb);
+                sch->qstats.backlog -= len;
                 kfree_skb(skb);
                 return len;
         }