From: Vasily Averin <vvs@parallels•com>
To: netdev@vger•kernel.org
Cc: Alexey Kuznetsov <kuznet@parallels•com>,
"David S. Miller" <davem@davemloft•net>,
Jamal Hadi Salim <jhs@mojatatu•com>
Subject: [PATCH 1/1] cbq: incorrect processing of high limits
Date: Mon, 01 Apr 2013 17:01:32 +0400 [thread overview]
Message-ID: <5159852C.8060003@parallels.com> (raw)
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>
---
net/sched/sch_cbq.c | 5 ++++-
1 files changed, 4 insertions(+), 1 deletions(-)
diff --git a/net/sched/sch_cbq.c b/net/sched/sch_cbq.c
index 6aabd77..5b5c83a 100644
--- a/net/sched/sch_cbq.c
+++ b/net/sched/sch_cbq.c
@@ -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 += incr;
q->now_rt = now;
for (;;) {
--
1.7.5.4
next reply other threads:[~2013-04-01 13:02 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-01 13:01 Vasily Averin [this message]
2013-04-01 16:24 ` [PATCH 1/1] cbq: incorrect processing of high limits Eric Dumazet
2013-04-02 18:30 ` David Miller
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