From: Dave Taht <[email protected]>

After queue lengths start getting out of hand, try to preserve memory
by shortening skbs to their truesize on the common pfifo, codel, and
fq_codel qdiscs.

Arguably (128) should be a configureable param
---
 ..._reduce_truesize-support-to-common-qdiscs.patch |   73 ++++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 
target/linux/generic/patches-3.3/057-net-add-skb_reduce_truesize-support-to-common-qdiscs.patch

diff --git 
a/target/linux/generic/patches-3.3/057-net-add-skb_reduce_truesize-support-to-common-qdiscs.patch
 
b/target/linux/generic/patches-3.3/057-net-add-skb_reduce_truesize-support-to-common-qdiscs.patch
new file mode 100644
index 0000000..d80e4ac
--- /dev/null
+++ 
b/target/linux/generic/patches-3.3/057-net-add-skb_reduce_truesize-support-to-common-qdiscs.patch
@@ -0,0 +1,73 @@
+From 341cca736cb9a991069d6ad4f819241161936f47 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Dave=20T=C3=A4ht?= <[email protected]>
+Date: Mon, 17 Sep 2012 19:20:22 -0700
+Subject: [PATCH 711/712] net: add skb_reduce_truesize support to common
+ qdiscs
+
+Reduce skb size under load when queues begin to fill on the
+common qdiscs.
+---
+ net/sched/sch_codel.c    |    2 ++
+ net/sched/sch_fifo.c     |   12 ++++++++----
+ net/sched/sch_fq_codel.c |    2 ++
+ 3 files changed, 12 insertions(+), 4 deletions(-)
+
+diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c
+index 2f9ab17..12d9363c 100644
+--- a/net/sched/sch_codel.c
++++ b/net/sched/sch_codel.c
+@@ -96,6 +96,8 @@ static int codel_qdisc_enqueue(struct sk_buff *skb, struct 
Qdisc *sch)
+       struct codel_sched_data *q;
+ 
+       if (likely(qdisc_qlen(sch) < sch->limit)) {
++              if(qdisc_qlen(sch) > 128)
++                      skb = skb_reduce_truesize(skb);
+               codel_set_enqueue_time(skb);
+               return qdisc_enqueue_tail(skb, sch);
+       }
+diff --git a/net/sched/sch_fifo.c b/net/sched/sch_fifo.c
+index 66effe2..2031a3e 100644
+--- a/net/sched/sch_fifo.c
++++ b/net/sched/sch_fifo.c
+@@ -29,17 +29,21 @@ static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc 
*sch)
+ 
+ static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch)
+ {
+-      if (likely(skb_queue_len(&sch->q) < sch->limit))
++      if (likely(skb_queue_len(&sch->q) < sch->limit)) {
++              if (skb_queue_len(&sch->q) > 128)
++                      skb = skb_reduce_truesize(skb);
+               return qdisc_enqueue_tail(skb, sch);
+-
++              }
+       return qdisc_reshape_fail(skb, sch);
+ }
+ 
+ static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch)
+ {
+-      if (likely(skb_queue_len(&sch->q) < sch->limit))
++      if (likely(skb_queue_len(&sch->q) < sch->limit)) {
++              if (skb_queue_len(&sch->q) > 128)
++                      skb = skb_reduce_truesize(skb);
+               return qdisc_enqueue_tail(skb, sch);
+-
++      }
+       /* queue full, remove one skb to fulfill the limit */
+       __qdisc_queue_drop_head(sch, &sch->q);
+       sch->qstats.drops++;
+diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c
+index ba944bd..136d2bc 100644
+--- a/net/sched/sch_fq_codel.c
++++ b/net/sched/sch_fq_codel.c
+@@ -182,6 +182,8 @@ static int fq_codel_enqueue(struct sk_buff *skb, struct 
Qdisc *sch)
+               return ret;
+       }
+       idx--;
++      if (sch->q.qlen > 128)
++              skb = skb_reduce_truesize(skb);
+ 
+       codel_set_enqueue_time(skb);
+       flow = &q->flows[idx];
+-- 
+1.7.9.5
+
-- 
1.7.9.5

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