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authorEric Dumazet <eric.dumazet@gmail.com>2010-05-06 21:58:51 -0700
committerDavid S. Miller <davem@davemloft.net>2010-05-06 21:58:51 -0700
commit18e8c134f4e984e6639e62846345192816f06d5c (patch)
tree81bb46de14f020424716bd41915e831b07ce00c6
parentd6bc0149d8f2300bffa03ea6fea3ca39744277a6 (diff)
net: Increase NET_SKB_PAD to 64 bytes
eth_type_trans() & get_rps_cpus() currently need two 64bytes cache lines in packet to compute rxhash. Increasing NET_SKB_PAD from 32 to 64 reduces the need to one cache line only, and makes RPS faster. NET_IP_ALIGN(2) + ethernet_header(14) + IP_header(20/40) + ports(8) Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--include/linux/skbuff.h5
1 files changed, 4 insertions, 1 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 88d55395a27c..c9525bce80f6 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1361,9 +1361,12 @@ static inline int skb_network_offset(const struct sk_buff *skb)
*
* Various parts of the networking layer expect at least 32 bytes of
* headroom, you should not reduce this.
+ * With RPS, we raised NET_SKB_PAD to 64 so that get_rps_cpus() fetches span
+ * a 64 bytes aligned block to fit modern (>= 64 bytes) cache line sizes
+ * NET_IP_ALIGN(2) + ethernet_header(14) + IP_header(20/40) + ports(8)
*/
#ifndef NET_SKB_PAD
-#define NET_SKB_PAD 32
+#define NET_SKB_PAD 64
#endif
extern int ___pskb_trim(struct sk_buff *skb, unsigned int len);