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-rw-r--r--target/linux/generic/patches-3.18/656-skb_reduce_truesize-helper.patch41
1 files changed, 41 insertions, 0 deletions
diff --git a/target/linux/generic/patches-3.18/656-skb_reduce_truesize-helper.patch b/target/linux/generic/patches-3.18/656-skb_reduce_truesize-helper.patch
new file mode 100644
index 0000000..b326a8b
--- /dev/null
+++ b/target/linux/generic/patches-3.18/656-skb_reduce_truesize-helper.patch
@@ -0,0 +1,41 @@
+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
+@@ -2068,6 +2068,24 @@ 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