From 18e8c134f4e984e6639e62846345192816f06d5c Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 6 May 2010 21:58:51 -0700 Subject: 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 Signed-off-by: David S. Miller --- include/linux/skbuff.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) 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); -- cgit v1.2.3