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authorVasily Averin <vvs@parallels.com>2014-08-14 12:27:47 +0400
committerDavid S. Miller <davem@davemloft.net>2014-08-19 10:58:44 -0700
commit73d0f37ac4ee5b60e6b9c1b3ccb8766bade9d9c5 (patch)
treeadaf72c8208c62eed0d4e6a74983cb8f6741ab03 /net/sched/sch_cbq.c
parentac32c7f705692b92fe12dcbe88fe87136fdfff6f (diff)
cbq: incorrectly low bandwidth setting blocks limited traffic
Mainstream commit f0f6ee1f70c4 ("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: f0f6ee1f70c4 ("cbq: incorrect processing of high limits") Signed-off-by: Vasily Averin <vvs@openvz.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched/sch_cbq.c')
-rw-r--r--net/sched/sch_cbq.c37
1 files changed, 13 insertions, 24 deletions
diff --git a/net/sched/sch_cbq.c b/net/sched/sch_cbq.c
index ead526467cca..550be9504fff 100644
--- a/net/sched/sch_cbq.c
+++ b/net/sched/sch_cbq.c
@@ -700,8 +700,13 @@ 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 +722,7 @@ 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 +766,7 @@ 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 +776,8 @@ 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);
@@ -943,30 +949,13 @@ 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 = now;
q->now_rt = now;
for (;;) {