From: Kevin Darbyshire-Bryant <kevin@darbyshire-bryant.me.uk>
Date: Sat, 7 May 2016 08:57:18 +0000 (+0100)
Subject: kernel: fq_codel match flows_cnt to limit sizing
X-Git-Tag: v17.01.0-rc1~2844
X-Git-Url: http://git.openwrt.org/?p=openwrt%2Fopenwrt.git;a=commitdiff_plain;h=e288e1bd3210c2025f6fc0dd9c338ea9dbf04bca;hp=374cae9e6fcaf4cf4de4f2095f3fec558da51df6

kernel: fq_codel match flows_cnt to limit sizing

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>
---

diff --git a/target/linux/generic/patches-3.18/660-fq_codel_defaults.patch b/target/linux/generic/patches-3.18/660-fq_codel_defaults.patch
index 8c99e62cec..e0f73dedb9 100644
--- a/target/linux/generic/patches-3.18/660-fq_codel_defaults.patch
+++ b/target/linux/generic/patches-3.18/660-fq_codel_defaults.patch
@@ -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);
diff --git a/target/linux/generic/patches-4.1/660-fq_codel_defaults.patch b/target/linux/generic/patches-4.1/660-fq_codel_defaults.patch
index 8c99e62cec..e0f73dedb9 100644
--- a/target/linux/generic/patches-4.1/660-fq_codel_defaults.patch
+++ b/target/linux/generic/patches-4.1/660-fq_codel_defaults.patch
@@ -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);
diff --git a/target/linux/generic/patches-4.4/660-fq_codel_defaults.patch b/target/linux/generic/patches-4.4/660-fq_codel_defaults.patch
index cf4ff6fb18..5d99cd7fb4 100644
--- a/target/linux/generic/patches-4.4/660-fq_codel_defaults.patch
+++ b/target/linux/generic/patches-4.4/660-fq_codel_defaults.patch
@@ -1,11 +1,13 @@
 --- a/net/sched/sch_fq_codel.c
 +++ b/net/sched/sch_fq_codel.c
-@@ -412,7 +412,7 @@ static int fq_codel_init(struct Qdisc *s
+@@ -412,8 +412,8 @@ 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);