kernel: add patches by Dave Täht to reduce buffer size in longer queues to reduce memory pressure

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

SVN-Revision: 36301
owl
Felix Fietkau 2013-04-10 13:11:16 +00:00
parent 915969ff2c
commit 307965026a
4 changed files with 208 additions and 0 deletions

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From 4593a806e31119c5bd3faa00c7210ad862d515af Mon Sep 17 00:00:00 2001
From: Dave Taht <dave.taht@bufferbloat.net>
Date: Mon, 31 Dec 2012 10:02:21 -0800
Subject: [PATCH 3/7] skb_reduce_truesize: helper function for shrinking skbs
whenever needed
On embedded devices in particular, large queues of small packets from the rx
path with a large truesize can exist. Reducing their size can reduce
memory pressure. skb_reduce_truesize is a helper function for doing this,
when needed.
---
include/linux/skbuff.h | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1772,6 +1772,24 @@ static inline void pskb_trim_unique(stru
BUG_ON(err);
}
+/*
+ * Caller wants to reduce memory needs before queueing skb
+ * The (expensive) copy should not be be done in fast path.
+ */
+static inline struct sk_buff *skb_reduce_truesize(struct sk_buff *skb)
+{
+ if (skb->truesize > 2 * SKB_TRUESIZE(skb->len)) {
+ struct sk_buff *nskb;
+ nskb = skb_copy_expand(skb, skb_headroom(skb), 0,
+ GFP_ATOMIC | __GFP_NOWARN);
+ if (nskb) {
+ __kfree_skb(skb);
+ skb = nskb;
+ }
+ }
+ return skb;
+}
+
/**
* skb_orphan - orphan a buffer
* @skb: buffer to orphan

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From bc9fec2f87d57bdbff30d296605e24504513f65c 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 4/7] 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(-)
--- a/net/sched/sch_codel.c
+++ b/net/sched/sch_codel.c
@@ -96,6 +96,8 @@ static int codel_qdisc_enqueue(struct sk
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);
}
--- a/net/sched/sch_fifo.c
+++ b/net/sched/sch_fifo.c
@@ -29,17 +29,21 @@ static int bfifo_enqueue(struct sk_buff
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++;
--- 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_bu
return ret;
}
idx--;
+ if (sch->q.qlen > 128)
+ skb = skb_reduce_truesize(skb);
codel_set_enqueue_time(skb);
flow = &q->flows[idx];

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From 4593a806e31119c5bd3faa00c7210ad862d515af Mon Sep 17 00:00:00 2001
From: Dave Taht <dave.taht@bufferbloat.net>
Date: Mon, 31 Dec 2012 10:02:21 -0800
Subject: [PATCH 3/7] skb_reduce_truesize: helper function for shrinking skbs
whenever needed
On embedded devices in particular, large queues of small packets from the rx
path with a large truesize can exist. Reducing their size can reduce
memory pressure. skb_reduce_truesize is a helper function for doing this,
when needed.
---
include/linux/skbuff.h | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1801,6 +1801,24 @@ static inline void pskb_trim_unique(stru
BUG_ON(err);
}
+/*
+ * Caller wants to reduce memory needs before queueing skb
+ * The (expensive) copy should not be be done in fast path.
+ */
+static inline struct sk_buff *skb_reduce_truesize(struct sk_buff *skb)
+{
+ if (skb->truesize > 2 * SKB_TRUESIZE(skb->len)) {
+ struct sk_buff *nskb;
+ nskb = skb_copy_expand(skb, skb_headroom(skb), 0,
+ GFP_ATOMIC | __GFP_NOWARN);
+ if (nskb) {
+ __kfree_skb(skb);
+ skb = nskb;
+ }
+ }
+ return skb;
+}
+
/**
* skb_orphan - orphan a buffer
* @skb: buffer to orphan

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From bc9fec2f87d57bdbff30d296605e24504513f65c 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 4/7] 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(-)
--- a/net/sched/sch_codel.c
+++ b/net/sched/sch_codel.c
@@ -96,6 +96,8 @@ static int codel_qdisc_enqueue(struct sk
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);
}
--- a/net/sched/sch_fifo.c
+++ b/net/sched/sch_fifo.c
@@ -29,17 +29,21 @@ static int bfifo_enqueue(struct sk_buff
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++;
--- 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_bu
return ret;
}
idx--;
+ if (sch->q.qlen > 128)
+ skb = skb_reduce_truesize(skb);
codel_set_enqueue_time(skb);
flow = &q->flows[idx];