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Merge branch 'cbq-fixes' 

Vasily Averin says:

====================
cbq: incorrectly low bandwidth blocks limited traffic

v2: patch description changes
Fixes: f0f6ee1f70 ("cbq: incorrect processing of high limits")

Mainstream commit f0f6ee1f70 ("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.

More detailed problem description can be found here:
http://www.spinics.net/lists/netdev/msg292493.html

Following patches should fix the problem.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2014-08-19 10:59:12 -07:00
parent ac32c7f705 7201c1ddf7
commit d3b6f9ffca
1 changed files with 13 additions and 33 deletions
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44
net/sched/sch_cbq.c
View File

@ -159,7 +159,6 @@ struct cbq_sched_data {
struct cbq_class *tx_borrowed;
int tx_len;
psched_time_t now; /* Cached timestamp */
psched_time_t now_rt; /* Cached real time */
unsigned int pmask;
struct hrtimer delay_timer;
@ -353,12 +352,7 @@ cbq_mark_toplevel(struct cbq_sched_data *q, struct cbq_class *cl)
int toplevel = q->toplevel;
if (toplevel > cl->level && !(qdisc_is_throttled(cl->q))) {
psched_time_t now;
psched_tdiff_t incr;
now = psched_get_time();
incr = now - q->now_rt;
now = q->now + incr;
psched_time_t now = psched_get_time();
do {
if (cl->undertime < now) {
@ -700,8 +694,13 @@ cbq_update(struct cbq_sched_data *q)
struct cbq_class *this = q->tx_class;
struct cbq_class *cl = this;
int len = q->tx_len;
psched_time_t now;
q->tx_class = NULL;
/* Time integrator. We calculate EOS time
* by adding expected packet transmission time.
*/
now = q->now + L2T(&q->link, len);
for ( ; cl; cl = cl->share) {
long avgidle = cl->avgidle;
@ -717,7 +716,7 @@ cbq_update(struct cbq_sched_data *q)
* idle = (now - last) - last_pktlen/rate
*/
idle = q->now - cl->last;
idle = now - cl->last;
if ((unsigned long)idle > 128*1024*1024) {
avgidle = cl->maxidle;
} else {
@ -761,7 +760,7 @@ cbq_update(struct cbq_sched_data *q)
idle -= L2T(&q->link, len);
idle += L2T(cl, len);
cl->undertime = q->now + idle;
cl->undertime = now + idle;
} else {
/* Underlimit */
@ -771,7 +770,8 @@ cbq_update(struct cbq_sched_data *q)
else
cl->avgidle = avgidle;
}
cl->last = q->now;
if ((s64)(now - cl->last) > 0)
cl->last = now;
}
cbq_update_toplevel(q, this, q->tx_borrowed);
@ -943,31 +943,13 @@ cbq_dequeue(struct Qdisc *sch)
struct sk_buff *skb;
struct cbq_sched_data *q = qdisc_priv(sch);
psched_time_t now;
psched_tdiff_t incr;
now = psched_get_time();
incr = now - q->now_rt;
if (q->tx_class) {
psched_tdiff_t incr2;
/* Time integrator. We calculate EOS time
* by adding expected packet transmission time.
* If real time is greater, we warp artificial clock,
* so that:
*
* cbq_time = max(real_time, work);
*/
incr2 = L2T(&q->link, q->tx_len);
q->now += incr2;
if (q->tx_class)
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 (;;) {
q->wd_expires = 0;
@ -1223,7 +1205,6 @@ cbq_reset(struct Qdisc *sch)
hrtimer_cancel(&q->delay_timer);
q->toplevel = TC_CBQ_MAXLEVEL;
q->now = psched_get_time();
q->now_rt = q->now;
for (prio = 0; prio <= TC_CBQ_MAXPRIO; prio++)
q->active[prio] = NULL;
@ -1407,7 +1388,6 @@ static int cbq_init(struct Qdisc *sch, struct nlattr *opt)
q->delay_timer.function = cbq_undelay;
q->toplevel = TC_CBQ_MAXLEVEL;
q->now = psched_get_time();
q->now_rt = q->now;
cbq_link_class(&q->link);