cbq: incorrectly low bandwidth setting blocks limited traffic
Mainstream commitf0f6ee1f70
("cbq: incorrect processing of high limits") have side effect: if cbq bandwidth setting is less than real interface throughput non-limited traffic can delay limited traffic for a very long time. This happen because of q->now changes incorrectly in cbq_dequeue(): in described scenario L2T is much greater than real time delay, and q->now gets an extra boost for each transmitted packet. Accumulated boost prevents update q->now, and blocked class can wait very long time until (q->now >= cl->undertime) will be true again. To fix the problem the patch updates q->now on each cbq_update() call. L2T-related pre-modification q->now was moved to cbq_update(). My testing confirmed that it fixes the problem and did not discover any side-effects Fixes:f0f6ee1f70
("cbq: incorrect processing of high limits") Signed-off-by: Vasily Averin <vvs@openvz.org> Signed-off-by: David S. Miller <davem@davemloft.net>
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ac32c7f705
Коммит
73d0f37ac4
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@ -700,8 +700,13 @@ cbq_update(struct cbq_sched_data *q)
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struct cbq_class *this = q->tx_class;
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struct cbq_class *cl = this;
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int len = q->tx_len;
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psched_time_t now;
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q->tx_class = NULL;
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/* Time integrator. We calculate EOS time
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* by adding expected packet transmission time.
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*/
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now = q->now + L2T(&q->link, len);
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for ( ; cl; cl = cl->share) {
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long avgidle = cl->avgidle;
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@ -717,7 +722,7 @@ cbq_update(struct cbq_sched_data *q)
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* idle = (now - last) - last_pktlen/rate
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*/
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idle = q->now - cl->last;
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idle = now - cl->last;
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if ((unsigned long)idle > 128*1024*1024) {
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avgidle = cl->maxidle;
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} else {
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@ -761,7 +766,7 @@ cbq_update(struct cbq_sched_data *q)
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idle -= L2T(&q->link, len);
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idle += L2T(cl, len);
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cl->undertime = q->now + idle;
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cl->undertime = now + idle;
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} else {
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/* Underlimit */
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@ -771,7 +776,8 @@ cbq_update(struct cbq_sched_data *q)
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else
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cl->avgidle = avgidle;
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}
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cl->last = q->now;
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if ((s64)(now - cl->last) > 0)
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cl->last = now;
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}
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cbq_update_toplevel(q, this, q->tx_borrowed);
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@ -943,30 +949,13 @@ cbq_dequeue(struct Qdisc *sch)
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struct sk_buff *skb;
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struct cbq_sched_data *q = qdisc_priv(sch);
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psched_time_t now;
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psched_tdiff_t incr;
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now = psched_get_time();
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incr = now - q->now_rt;
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if (q->tx_class) {
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psched_tdiff_t incr2;
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/* Time integrator. We calculate EOS time
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* by adding expected packet transmission time.
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* If real time is greater, we warp artificial clock,
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* so that:
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*
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* cbq_time = max(real_time, work);
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*/
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incr2 = L2T(&q->link, q->tx_len);
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q->now += incr2;
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if (q->tx_class)
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cbq_update(q);
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if ((incr -= incr2) < 0)
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incr = 0;
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q->now += incr;
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} else {
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if (now > q->now)
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q->now = now;
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}
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q->now = now;
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q->now_rt = now;
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for (;;) {
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