kernel: update 3.18 to 3.18.14
[openwrt/svn-archive/archive.git] / target / linux / generic / patches-3.18 / 656-skb_reduce_truesize-helper.patch
1 From 4593a806e31119c5bd3faa00c7210ad862d515af Mon Sep 17 00:00:00 2001
2 From: Dave Taht <dave.taht@bufferbloat.net>
3 Date: Mon, 31 Dec 2012 10:02:21 -0800
4 Subject: [PATCH 3/7] skb_reduce_truesize: helper function for shrinking skbs
5 whenever needed
6
7 On embedded devices in particular, large queues of small packets from the rx
8 path with a large truesize can exist. Reducing their size can reduce
9 memory pressure. skb_reduce_truesize is a helper function for doing this,
10 when needed.
11 ---
12 include/linux/skbuff.h | 18 ++++++++++++++++++
13 1 file changed, 18 insertions(+)
14
15 --- a/include/linux/skbuff.h
16 +++ b/include/linux/skbuff.h
17 @@ -2068,6 +2068,24 @@ static inline void pskb_trim_unique(stru
18 BUG_ON(err);
19 }
20
21 +/*
22 + * Caller wants to reduce memory needs before queueing skb
23 + * The (expensive) copy should not be be done in fast path.
24 + */
25 +static inline struct sk_buff *skb_reduce_truesize(struct sk_buff *skb)
26 +{
27 + if (skb->truesize > 2 * SKB_TRUESIZE(skb->len)) {
28 + struct sk_buff *nskb;
29 + nskb = skb_copy_expand(skb, skb_headroom(skb), 0,
30 + GFP_ATOMIC | __GFP_NOWARN);
31 + if (nskb) {
32 + __kfree_skb(skb);
33 + skb = nskb;
34 + }
35 + }
36 + return skb;
37 +}
38 +
39 /**
40 * skb_orphan - orphan a buffer
41 * @skb: buffer to orphan