Commit f0f6ee1f authored Apr 01, 2013 by Vasily Averin Committed by David S. Miller Apr 02, 2013

cbq: incorrect processing of high limits



currently cbq works incorrectly for limits > 10% real link bandwidth,
and practically does not work for limits > 50% real link bandwidth.
Below are results of experiments taken on 1 Gbit link

 In shaper | Actual Result
-----------+---------------
  100M     | 108 Mbps
  200M     | 244 Mbps
  300M     | 412 Mbps
  500M     | 893 Mbps

This happen because of q->now changes incorrectly in cbq_dequeue():
when it is called before real end of packet transmitting,
L2T is greater than real time delay, q_now gets an extra boost
but never compensate it.

To fix this problem we prevent change of q->now until its synchronization
with real time.

Signed-off-by: Vasily Averin <vvs@openvz.org>
Reviewed-by: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent bab6a9ea

net/sched/sch_cbq.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -962,8 +962,11 @@ cbq_dequeue(struct Qdisc *sch)
		cbq_update(q);
		if ((incr -= incr2) < 0)
		incr = 0;
		}
		q->now += incr;
		} else {
		if (now > q->now)
		q->now = now;
		}
		q->now_rt = now;

		for (;;) {