Thread (1 message) 1 message, 1 author, 2013-05-24

[PATCH net-next v5 1/2] net: Use 16bits for *_headers fields of struct skbuff

From: Simon Horman <hidden>
Date: 2013-05-24 07:02:51
Subsystem: networking [general], the rest · Maintainers: "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds

Possibly related (same subject, not in this thread)

In order to mitigate ongoing incresase in the size of struct skbuff
use 16 bit integer offsets rather than pointers for inner_*_headers.

This appears to reduce the size of struct skbuff from 0xd0 to 0xc0
bytes on x86_64 with the following all unset.

	CONFIG_XFRM
	CONFIG_NF_CONNTRACK
	CONFIG_NF_CONNTRACK_MODULE
	NET_SKBUFF_NF_DEFRAG_NEEDED
	CONFIG_BRIDGE_NETFILTER
	CONFIG_NET_SCHED
	CONFIG_IPV6_NDISC_NODETYPE
	CONFIG_NET_DMA
	CONFIG_NETWORK_SECMARK

Signed-off-by: Simon Horman <horms-/R6kz+dDXgpPR4JQBCEnsQ@public.gmane.org>
---
 include/linux/skbuff.h | 119 +++----------------------------------------------
 1 file changed, 6 insertions(+), 113 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2e0ced1..5663e35 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -509,12 +509,12 @@ struct sk_buff {
 		__u32		reserved_tailroom;
 	};
 
-	sk_buff_data_t		inner_transport_header;
-	sk_buff_data_t		inner_network_header;
-	sk_buff_data_t		inner_mac_header;
-	sk_buff_data_t		transport_header;
-	sk_buff_data_t		network_header;
-	sk_buff_data_t		mac_header;
+	__u16			inner_transport_header;
+	__u16			inner_network_header;
+	__u16			inner_mac_header;
+	__u16			transport_header;
+	__u16			network_header;
+	__u16			mac_header;
 	/* These elements must be at the end, see alloc_skb() for details.  */
 	sk_buff_data_t		tail;
 	sk_buff_data_t		end;
@@ -1527,7 +1527,6 @@ static inline void skb_reset_mac_len(struct sk_buff *skb)
 	skb->mac_len = skb->network_header - skb->mac_header;
 }
 
-#ifdef NET_SKBUFF_DATA_USES_OFFSET
 static inline unsigned char *skb_inner_transport_header(const struct sk_buff
 							*skb)
 {
@@ -1638,112 +1637,6 @@ static inline void skb_set_mac_header(struct sk_buff *skb, const int offset)
 	skb->mac_header += offset;
 }
 
-#else /* NET_SKBUFF_DATA_USES_OFFSET */
-static inline unsigned char *skb_inner_transport_header(const struct sk_buff
-							*skb)
-{
-	return skb->inner_transport_header;
-}
-
-static inline void skb_reset_inner_transport_header(struct sk_buff *skb)
-{
-	skb->inner_transport_header = skb->data;
-}
-
-static inline void skb_set_inner_transport_header(struct sk_buff *skb,
-						   const int offset)
-{
-	skb->inner_transport_header = skb->data + offset;
-}
-
-static inline unsigned char *skb_inner_network_header(const struct sk_buff *skb)
-{
-	return skb->inner_network_header;
-}
-
-static inline void skb_reset_inner_network_header(struct sk_buff *skb)
-{
-	skb->inner_network_header = skb->data;
-}
-
-static inline void skb_set_inner_network_header(struct sk_buff *skb,
-						const int offset)
-{
-	skb->inner_network_header = skb->data + offset;
-}
-
-static inline unsigned char *skb_inner_mac_header(const struct sk_buff *skb)
-{
-	return skb->inner_mac_header;
-}
-
-static inline void skb_reset_inner_mac_header(struct sk_buff *skb)
-{
-	skb->inner_mac_header = skb->data;
-}
-
-static inline void skb_set_inner_mac_header(struct sk_buff *skb,
-						const int offset)
-{
-	skb->inner_mac_header = skb->data + offset;
-}
-static inline bool skb_transport_header_was_set(const struct sk_buff *skb)
-{
-	return skb->transport_header != NULL;
-}
-
-static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
-{
-	return skb->transport_header;
-}
-
-static inline void skb_reset_transport_header(struct sk_buff *skb)
-{
-	skb->transport_header = skb->data;
-}
-
-static inline void skb_set_transport_header(struct sk_buff *skb,
-					    const int offset)
-{
-	skb->transport_header = skb->data + offset;
-}
-
-static inline unsigned char *skb_network_header(const struct sk_buff *skb)
-{
-	return skb->network_header;
-}
-
-static inline void skb_reset_network_header(struct sk_buff *skb)
-{
-	skb->network_header = skb->data;
-}
-
-static inline void skb_set_network_header(struct sk_buff *skb, const int offset)
-{
-	skb->network_header = skb->data + offset;
-}
-
-static inline unsigned char *skb_mac_header(const struct sk_buff *skb)
-{
-	return skb->mac_header;
-}
-
-static inline int skb_mac_header_was_set(const struct sk_buff *skb)
-{
-	return skb->mac_header != NULL;
-}
-
-static inline void skb_reset_mac_header(struct sk_buff *skb)
-{
-	skb->mac_header = skb->data;
-}
-
-static inline void skb_set_mac_header(struct sk_buff *skb, const int offset)
-{
-	skb->mac_header = skb->data + offset;
-}
-#endif /* NET_SKBUFF_DATA_USES_OFFSET */
-
 static inline void skb_probe_transport_header(struct sk_buff *skb,
 					      const int offset_hint)
 {
-- 
1.8.2.1
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