qdiscs: add reduce_truesize support to common qdiscs

The reduce truesize patches help with memory lossage under load,
at the price of performance. Given a choice between slowing down
or running out of memory, I'd rather slow down.

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?= <dave.taht@bufferbloat.net>
+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
+commont 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) > 64)
++			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) > 64)
++			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) > 64)
++			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 > 64)
++		skb = skb_reduce_truesize(skb);
+
+ 	codel_set_enqueue_time(skb);
+ 	flow = &q->flows[idx];
+-- 
+1.7.9.5
+