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kernel: fq_codel match flows_cnt to limit sizing

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OpenWRT changed the default fq_codel sch->limit from 10240 to 1024,
without also adjusting q->flows_cnt.  Eric Dumazet explains below that
you must also adjust the buckets (q->flows_cnt) for this not to break.

Eric explains: Limit of 1024 packets and 1024 flows is not wise I think.
(If all buckets are in use, each bucket has a virtual queue of 1 packet,
which is almost the same than having no queue at all)

I suggest to have at least 8 packets per bucket, to let Codel have a
chance to trigger.  So you could either reduce number of buckets to 128
(if memory is tight), or increase limit to 8192.

flows_cnt is now set to 1024/8=128

Signed-off-by: Kevin Darbyshire-Bryant <kevin@darbyshire-bryant.me.uk>
This commit is contained in:
Kevin Darbyshire-Bryant
2016-05-07 09:57:18 +01:00
committed by John Crispin
parent 374cae9e6f
commit e288e1bd32
3 changed files with 12 additions and 6 deletions
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6
target/linux/generic/patches-3.18/660-fq_codel_defaults.patch
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@@ -1,11 +1,13 @@
--- a/net/sched/sch_fq_codel.c
+++ b/net/sched/sch_fq_codel.c
@@ -387,7 +387,7 @@ static int fq_codel_init(struct Qdisc *s
@@ -387,8 +387,8 @@ static int fq_codel_init(struct Qdisc *s
struct fq_codel_sched_data *q = qdisc_priv(sch);
int i;
- sch->limit = 10*1024;
- q->flows_cnt = 1024;
+ sch->limit = 1024;
q->flows_cnt = 1024;
+ q->flows_cnt = 128;
q->quantum = psched_mtu(qdisc_dev(sch));
q->perturbation = prandom_u32();
INIT_LIST_HEAD(&q->new_flows);