net: Increase NET_SKB_PAD to 64 bytes (18e8c134) · Commits · 戴 / test

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>

include/linux/skbuff.h

+4 −1

Original line number	Diff line number	Diff line
		@@ -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);

Admin message