| From: Vasily Averin <vvs@parallels.com> |
| Date: Mon, 1 Apr 2013 03:01:32 +0000 |
| Subject: cbq: incorrect processing of high limits |
| |
| [ Upstream commit f0f6ee1f70c4eaab9d52cf7d255df4bd89f8d1c2 ] |
| |
| 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> |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| net/sched/sch_cbq.c | 5 ++++- |
| 1 file changed, 4 insertions(+), 1 deletion(-) |
| |
| --- a/net/sched/sch_cbq.c |
| +++ b/net/sched/sch_cbq.c |
| @@ -963,8 +963,11 @@ 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 += incr; |
| q->now_rt = now; |
| |
| for (;;) { |
