[SK_BUFF]: Convert skb->tail to sk_buff_data_t
So that it is also an offset from skb->head, reduces its size from 8 to 4 bytes
on 64bit architectures, allowing us to combine the 4 bytes hole left by the
layer headers conversion, reducing struct sk_buff size to 256 bytes, i.e. 4
64byte cachelines, and since the sk_buff slab cache is SLAB_HWCACHE_ALIGN...
:-)
Many calculations that previously required that skb->{transport,network,
mac}_header be first converted to a pointer now can be done directly, being
meaningful as offsets or pointers.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2e74055..e1c2392 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -246,9 +246,6 @@
int iif;
/* 4 byte hole on 64 bit*/
- sk_buff_data_t transport_header;
- sk_buff_data_t network_header;
- sk_buff_data_t mac_header;
struct dst_entry *dst;
struct sec_path *sp;
@@ -303,13 +300,16 @@
__u32 mark;
+ sk_buff_data_t transport_header;
+ sk_buff_data_t network_header;
+ sk_buff_data_t mac_header;
/* These elements must be at the end, see alloc_skb() for details. */
- unsigned int truesize;
- atomic_t users;
+ sk_buff_data_t tail;
unsigned char *head,
*data,
- *tail,
*end;
+ unsigned int truesize;
+ atomic_t users;
};
#ifdef __KERNEL__
@@ -812,12 +812,45 @@
#define SKB_FRAG_ASSERT(skb) BUG_ON(skb_shinfo(skb)->frag_list)
#define SKB_LINEAR_ASSERT(skb) BUG_ON(skb_is_nonlinear(skb))
+#ifdef NET_SKBUFF_DATA_USES_OFFSET
+static inline unsigned char *skb_tail_pointer(const struct sk_buff *skb)
+{
+ return skb->head + skb->tail;
+}
+
+static inline void skb_reset_tail_pointer(struct sk_buff *skb)
+{
+ skb->tail = skb->data - skb->head;
+}
+
+static inline void skb_set_tail_pointer(struct sk_buff *skb, const int offset)
+{
+ skb_reset_tail_pointer(skb);
+ skb->tail += offset;
+}
+#else /* NET_SKBUFF_DATA_USES_OFFSET */
+static inline unsigned char *skb_tail_pointer(const struct sk_buff *skb)
+{
+ return skb->tail;
+}
+
+static inline void skb_reset_tail_pointer(struct sk_buff *skb)
+{
+ skb->tail = skb->data;
+}
+
+static inline void skb_set_tail_pointer(struct sk_buff *skb, const int offset)
+{
+ skb->tail = skb->data + offset;
+}
+#endif /* NET_SKBUFF_DATA_USES_OFFSET */
+
/*
* Add data to an sk_buff
*/
static inline unsigned char *__skb_put(struct sk_buff *skb, unsigned int len)
{
- unsigned char *tmp = skb->tail;
+ unsigned char *tmp = skb_tail_pointer(skb);
SKB_LINEAR_ASSERT(skb);
skb->tail += len;
skb->len += len;
@@ -835,11 +868,11 @@
*/
static inline unsigned char *skb_put(struct sk_buff *skb, unsigned int len)
{
- unsigned char *tmp = skb->tail;
+ unsigned char *tmp = skb_tail_pointer(skb);
SKB_LINEAR_ASSERT(skb);
skb->tail += len;
skb->len += len;
- if (unlikely(skb->tail>skb->end))
+ if (unlikely(skb_tail_pointer(skb) > skb->end))
skb_over_panic(skb, len, current_text_addr());
return tmp;
}
@@ -935,7 +968,7 @@
*/
static inline int skb_tailroom(const struct sk_buff *skb)
{
- return skb_is_nonlinear(skb) ? 0 : skb->end - skb->tail;
+ return skb_is_nonlinear(skb) ? 0 : skb->end - skb_tail_pointer(skb);
}
/**
@@ -1127,8 +1160,8 @@
WARN_ON(1);
return;
}
- skb->len = len;
- skb->tail = skb->data + len;
+ skb->len = len;
+ skb_set_tail_pointer(skb, len);
}
/**