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authorEric Dumazet <edumazet@google.com>2015-04-30 09:40:40 -0700
committerDavid S. Miller <davem@davemloft.net>2015-05-03 22:17:40 -0400
commita5d28090405038ca1f40c13f38d6d4285456efee (patch)
tree0ed77966629db018afd676eaec2e9dee99c79705 /net
parent6c3c1eb3c35e8856d6dcb01b412316a676f58bbe (diff)
downloadkernel-a5d28090405038ca1f40c13f38d6d4285456efee.tar.gz
codel: fix maxpacket/mtu confusion
Under presence of TSO/GSO/GRO packets, codel at low rates can be quite useless. In following example, not a single packet was ever dropped, while average delay in codel queue is ~100 ms ! qdisc codel 0: parent 1:12 limit 16000p target 5.0ms interval 100.0ms Sent 134376498 bytes 88797 pkt (dropped 0, overlimits 0 requeues 0) backlog 13626b 3p requeues 0 count 0 lastcount 0 ldelay 96.9ms drop_next 0us maxpacket 9084 ecn_mark 0 drop_overlimit 0 This comes from a confusion of what should be the minimal backlog. It is pretty clear it is not 64KB or whatever max GSO packet ever reached the qdisc. codel intent was to use MTU of the device. After the fix, we finally drop some packets, and rtt/cwnd of my single TCP flow are meeting our expectations. qdisc codel 0: parent 1:12 limit 16000p target 5.0ms interval 100.0ms Sent 102798497 bytes 67912 pkt (dropped 1365, overlimits 0 requeues 0) backlog 6056b 3p requeues 0 count 1 lastcount 1 ldelay 36.3ms drop_next 0us maxpacket 10598 ecn_mark 0 drop_overlimit 0 Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Kathleen Nichols <nichols@pollere.com> Cc: Dave Taht <dave.taht@gmail.com> Cc: Van Jacobson <vanj@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/sched/sch_codel.c2
-rw-r--r--net/sched/sch_fq_codel.c2
2 files changed, 2 insertions, 2 deletions
diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c
index de28f8e968e8..7a0bdb16ac92 100644
--- a/net/sched/sch_codel.c
+++ b/net/sched/sch_codel.c
@@ -164,7 +164,7 @@ static int codel_init(struct Qdisc *sch, struct nlattr *opt)
sch->limit = DEFAULT_CODEL_LIMIT;
- codel_params_init(&q->params);
+ codel_params_init(&q->params, sch);
codel_vars_init(&q->vars);
codel_stats_init(&q->stats);
diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c
index 1e52decb7b59..c244c45b78d7 100644
--- a/net/sched/sch_fq_codel.c
+++ b/net/sched/sch_fq_codel.c
@@ -391,7 +391,7 @@ static int fq_codel_init(struct Qdisc *sch, struct nlattr *opt)
q->perturbation = prandom_u32();
INIT_LIST_HEAD(&q->new_flows);
INIT_LIST_HEAD(&q->old_flows);
- codel_params_init(&q->cparams);
+ codel_params_init(&q->cparams, sch);
codel_stats_init(&q->cstats);
q->cparams.ecn = true;