2013-05-19 18:36:15 +00:00
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From 4593a806e31119c5bd3faa00c7210ad862d515af Mon Sep 17 00:00:00 2001
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From: Dave Taht <dave.taht@bufferbloat.net>
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Date: Mon, 31 Dec 2012 10:02:21 -0800
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Subject: [PATCH 3/7] skb_reduce_truesize: helper function for shrinking skbs
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whenever needed
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On embedded devices in particular, large queues of small packets from the rx
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path with a large truesize can exist. Reducing their size can reduce
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memory pressure. skb_reduce_truesize is a helper function for doing this,
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when needed.
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---
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include/linux/skbuff.h | 18 ++++++++++++++++++
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1 file changed, 18 insertions(+)
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--- a/include/linux/skbuff.h
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+++ b/include/linux/skbuff.h
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2013-12-15 19:16:30 +00:00
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@@ -1889,6 +1889,24 @@ static inline void pskb_trim_unique(stru
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2013-05-19 18:36:15 +00:00
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BUG_ON(err);
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}
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+/*
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+ * Caller wants to reduce memory needs before queueing skb
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+ * The (expensive) copy should not be be done in fast path.
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+ */
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+static inline struct sk_buff *skb_reduce_truesize(struct sk_buff *skb)
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+{
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+ if (skb->truesize > 2 * SKB_TRUESIZE(skb->len)) {
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+ struct sk_buff *nskb;
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+ nskb = skb_copy_expand(skb, skb_headroom(skb), 0,
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+ GFP_ATOMIC | __GFP_NOWARN);
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+ if (nskb) {
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+ __kfree_skb(skb);
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+ skb = nskb;
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+ }
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+ }
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+ return skb;
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+}
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+
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/**
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* skb_orphan - orphan a buffer
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* @skb: buffer to orphan
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