kernel: add a few patches for avoiding unnecessary skb reallocations - significantly improves ethernet<->wireless performance with mac80211 based drivers

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@31886 3c298f89-4303-0410-b956-a3cf2f4a3e73

3 files changed, 59 insertions, 0 deletions

diff --git a/target/linux/generic/patches-3.3/653-disable_netlink_trim.patch b/target/linux/generic/patches-3.3/653-disable_netlink_trim.patch
new file mode 100644
index 000000000..c6c7c75a9
--- /dev/null
+++ b/target/linux/generic/patches-3.3/653-disable_netlink_trim.patch
@@ -0,0 +1,28 @@
+--- a/net/netlink/af_netlink.c
++++ b/net/netlink/af_netlink.c
+@@ -854,25 +854,7 @@ void netlink_detachskb(struct sock *sk, 
+ 
+ static struct sk_buff *netlink_trim(struct sk_buff *skb, gfp_t allocation)
+ {
+-	int delta;
+-
+ 	skb_orphan(skb);
+-
+-	delta = skb->end - skb->tail;
+-	if (delta * 2 < skb->truesize)
+-		return skb;
+-
+-	if (skb_shared(skb)) {
+-		struct sk_buff *nskb = skb_clone(skb, allocation);
+-		if (!nskb)
+-			return skb;
+-		kfree_skb(skb);
+-		skb = nskb;
+-	}
+-
+-	if (!pskb_expand_head(skb, 0, -delta, allocation))
+-		skb->truesize -= delta;
+-
+ 	return skb;
+ }
+ 
diff --git a/target/linux/generic/patches-3.3/654-avoid_skb_cow_realloc.patch b/target/linux/generic/patches-3.3/654-avoid_skb_cow_realloc.patch
new file mode 100644
index 000000000..dfa98198e
--- /dev/null
+++ b/target/linux/generic/patches-3.3/654-avoid_skb_cow_realloc.patch
@@ -0,0 +1,20 @@
+--- a/include/linux/skbuff.h
++++ b/include/linux/skbuff.h
+@@ -1850,12 +1850,15 @@ static inline int skb_clone_writable(con
+ static inline int __skb_cow(struct sk_buff *skb, unsigned int headroom,
+ 			    int cloned)
+ {
++	unsigned int alloc_headroom = headroom;
+ 	int delta = 0;
+ 
+ 	if (headroom < NET_SKB_PAD)
+-		headroom = NET_SKB_PAD;
+-	if (headroom > skb_headroom(skb))
++		alloc_headroom = NET_SKB_PAD;
++	if (headroom > skb_headroom(skb) ||
++	    (cloned && alloc_headroom > skb_headroom(skb))) {
+ 		delta = headroom - skb_headroom(skb);
++	}
+ 
+ 	if (delta || cloned)
+ 		return pskb_expand_head(skb, ALIGN(delta, NET_SKB_PAD), 0,
diff --git a/target/linux/generic/patches-3.3/655-increase_skb_pad.patch b/target/linux/generic/patches-3.3/655-increase_skb_pad.patch
new file mode 100644
index 000000000..5d14daadf
--- /dev/null
+++ b/target/linux/generic/patches-3.3/655-increase_skb_pad.patch
@@ -0,0 +1,11 @@
+--- a/include/linux/skbuff.h
++++ b/include/linux/skbuff.h
+@@ -1558,7 +1558,7 @@ static inline int pskb_network_may_pull(
+  * NET_IP_ALIGN(2) + ethernet_header(14) + IP_header(20/40) + ports(8)
+  */
+ #ifndef NET_SKB_PAD
+-#define NET_SKB_PAD	max(32, L1_CACHE_BYTES)
++#define NET_SKB_PAD	max(48, L1_CACHE_BYTES)
+ #endif
+ 
+ extern int ___pskb_trim(struct sk_buff *skb, unsigned int len);