netdev - Re: [PATCH] netem: fix rate extension and drop accounting

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Date:	Tue, 17 Jul 2012 07:12:27 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Hagen Paul Pfeifer <hagen@...u.net>
Cc:	Mark Gordon <msg@...gle.com>, David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Yuchung Cheng <ycheng@...gle.com>,
	Andreas Terzis <aterzis@...gle.com>
Subject: Re: [PATCH] netem: fix rate extension and drop accounting

On Tue, 2012-07-17 at 01:26 +0200, Hagen Paul Pfeifer wrote:

> As Eric said: there are problems in combination with a static delay. During
> rate extension development we tested the raw/vanilla "rate" functionality.
> The rate part works faultless[TM] - at least independet of any other
> "delay-latency generator".

Well, to get correct rate, I use the following unofficial patch :

(Or else, the rate is really wrong)



diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index c412ad0..2740a75 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -433,16 +433,8 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 
 			delay += packet_len_2_sched_time(skb->len, q);
 
-			if (!skb_queue_empty(list)) {
-				/*
-				 * Last packet in queue is reference point (now).
-				 * First packet in queue is already in flight,
-				 * calculate this time bonus and substract
-				 * from delay.
-				 */
-				delay -= now - netem_skb_cb(skb_peek(list))->time_to_send;
+			if (!skb_queue_empty(list))
 				now = netem_skb_cb(skb_peek_tail(list))->time_to_send;
-			}
 		}
 
 		cb->time_to_send = now + delay;


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