Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [ 18/34] cbq: incorrect processing of high limits | Date | Mon, 29 Apr 2013 12:02:25 -0700 |
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3.4-stable review patch. If anyone has any objections, please let me know.
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From: Vasily Averin <vvs@parallels.com>
[ 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- 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 (;;) {
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