The following commit has been merged in the batman-adv/next branch: commit 425f09ab7d1c9da6ca4137dd639cb6fe3f8a88f3 Author: Eric Dumazet edumazet@google.com Date: Tue Aug 7 02:19:56 2012 +0000

net: output path optimizations

1) Avoid dirtying neighbour's confirmed field.

TCP workloads hits this cache line for each incoming ACK. Lets write n->confirmed only if there is a jiffie change.

2) Optimize neigh_hh_output() for the common Ethernet case, were hh_len is less than 16 bytes. Replace the memcpy() call by two inlined 64bit load/stores on x86_64.

Bench results using udpflood test, with -C option (MSG_CONFIRM flag added to sendto(), to reproduce the n->confirmed dirtying on UDP)

24 threads doing 1.000.000 UDP sendto() on dummy device, 4 runs.

before : 2.247s, 2.235s, 2.247s, 2.318s after : 1.884s, 1.905s, 1.891s, 1.895s

Signed-off-by: Eric Dumazet edumazet@google.com Signed-off-by: David S. Miller davem@davemloft.net

diff --git a/include/net/dst.h b/include/net/dst.h index baf5978..77f52f7 100644 --- a/include/net/dst.h +++ b/include/net/dst.h @@ -396,11 +396,15 @@ static inline void dst_confirm(struct dst_entry *dst) static inline int dst_neigh_output(struct dst_entry *dst, struct neighbour *n, struct sk_buff *skb) { - struct hh_cache *hh; + const struct hh_cache *hh; + + if (dst->pending_confirm) { + unsigned long now = jiffies;

- if (unlikely(dst->pending_confirm)) { - n->confirmed = jiffies; dst->pending_confirm = 0; + /* avoid dirtying neighbour */ + if (n->confirmed != now) + n->confirmed = now; }

hh = &n->hh; diff --git a/include/net/neighbour.h b/include/net/neighbour.h index 344d898..0dab173 100644 --- a/include/net/neighbour.h +++ b/include/net/neighbour.h @@ -334,18 +334,22 @@ static inline int neigh_hh_bridge(struct hh_cache *hh, struct sk_buff *skb) } #endif

-static inline int neigh_hh_output(struct hh_cache *hh, struct sk_buff *skb) +static inline int neigh_hh_output(const struct hh_cache *hh, struct sk_buff *skb) { unsigned int seq; int hh_len;

do { - int hh_alen; - seq = read_seqbegin(&hh->hh_lock); hh_len = hh->hh_len; - hh_alen = HH_DATA_ALIGN(hh_len); - memcpy(skb->data - hh_alen, hh->hh_data, hh_alen); + if (likely(hh_len <= HH_DATA_MOD)) { + /* this is inlined by gcc */ + memcpy(skb->data - HH_DATA_MOD, hh->hh_data, HH_DATA_MOD); + } else { + int hh_alen = HH_DATA_ALIGN(hh_len); + + memcpy(skb->data - hh_alen, hh->hh_data, hh_alen); + } } while (read_seqretry(&hh->hh_lock, seq));

skb_push(skb, hh_len);