From: Peilin Ye <peilin.ye@xxxxxxxxxxxxx>
Recently we introduced a Qdisc backpressure infrastructure (currently
supports UDP sockets). Use it in HTB Qdisc.
Tested with 500 Mbits/sec rate limit using 16 iperf UDP 1 Gbit/sec
clients. Before:
[ 3] 0.0-15.0 sec 54.2 MBytes 30.4 Mbits/sec 0.875 ms 1245750/1284444 (97%)
[ 3] 0.0-15.0 sec 54.2 MBytes 30.3 Mbits/sec 1.288 ms 1238753/1277402 (97%)
[ 3] 0.0-15.0 sec 54.8 MBytes 30.6 Mbits/sec 1.761 ms 1261762/1300817 (97%)
[ 3] 0.0-15.0 sec 53.9 MBytes 30.1 Mbits/sec 1.635 ms 1241690/1280133 (97%)
<...> ^^^^^^^^^^^^^^^^^^^^^
Total throughput is 482.0 Mbits/sec and average drop rate is 97.0%.
Now enable Qdisc backpressure for UDP sockets, with
udp_backpressure_interval default to 100 milliseconds:
[ 3] 0.0-15.0 sec 53.0 MBytes 29.6 Mbits/sec 1.621 ms 54/37856 (0.14%)
[ 3] 0.0-15.0 sec 55.9 MBytes 31.3 Mbits/sec 1.368 ms 6/39895 (0.015%)
[ 3] 0.0-15.0 sec 52.3 MBytes 29.2 Mbits/sec 1.560 ms 56/37340 (0.15%)
[ 3] 0.0-15.0 sec 52.7 MBytes 29.5 Mbits/sec 1.495 ms 57/37677 (0.15%)
<...> ^^^^^^^^^^^^^^^^
Total throughput is 485.9 Mbits/sec (0.81% higher) and average drop rate
is 0.1% (99.9% lower).
Fairness between flows is slightly affected, with per-flow average
throughput ranging from 29.2 to 31.8 Mbits/sec (compared with 29.7 to
30.6 Mbits/sec).
Signed-off-by: Peilin Ye <peilin.ye@xxxxxxxxxxxxx>
---
net/sched/sch_htb.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 23a9d6242429..e337b3d0dab3 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -623,6 +623,7 @@ static int htb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
__qdisc_enqueue_tail(skb, &q->direct_queue);
q->direct_pkts++;
} else {
+ qdisc_backpressure(skb);
return qdisc_drop(skb, sch, to_free);
}
#ifdef CONFIG_NET_CLS_ACT
@@ -634,6 +635,7 @@ static int htb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
#endif
} else if ((ret = qdisc_enqueue(skb, cl->leaf.q,
to_free)) != NET_XMIT_SUCCESS) {
+ qdisc_backpressure(skb);
if (net_xmit_drop_count(ret)) {
qdisc_qstats_drop(sch);
cl->drops++;
--
2.20.1
