Sending IPv6 udp packets on non connected sockets is quite slow, because ipv6_dev_get_saddr() is still using an rwlock and silly references games on ifa.
Tested: $ ./super_netperf 16 -H 4444::555:0786 -l 2000 -t UDP_STREAM -- -m 100 & [1] 12527 Performance is boosted from 2.02 Mpps to 4.28 Mpps Kernel profile before patches : 22.62% [kernel] [k] _raw_read_lock_bh 7.04% [kernel] [k] refcount_sub_and_test 6.56% [kernel] [k] ipv6_get_saddr_eval 5.67% [kernel] [k] _raw_read_unlock_bh 5.34% [kernel] [k] __ipv6_dev_get_saddr 4.95% [kernel] [k] refcount_inc_not_zero 4.03% [kernel] [k] __ip6addrlbl_match 3.70% [kernel] [k] _raw_spin_lock 3.44% [kernel] [k] ipv6_dev_get_saddr 3.24% [kernel] [k] ip6_pol_route 3.06% [kernel] [k] refcount_add_not_zero 2.30% [kernel] [k] __local_bh_enable_ip 1.81% [kernel] [k] mlx4_en_xmit 1.20% [kernel] [k] __ip6_append_data 1.12% [kernel] [k] __ip6_make_skb 1.11% [kernel] [k] __dev_queue_xmit 1.06% [kernel] [k] l3mdev_master_ifindex_rcu Kernel profile after patches : 11.36% [kernel] [k] ip6_pol_route 7.65% [kernel] [k] _raw_spin_lock 7.16% [kernel] [k] __ipv6_dev_get_saddr 6.49% [kernel] [k] ipv6_get_saddr_eval 6.04% [kernel] [k] refcount_add_not_zero 3.34% [kernel] [k] __ip6addrlbl_match 2.62% [kernel] [k] __dev_queue_xmit 2.37% [kernel] [k] mlx4_en_xmit 2.26% [kernel] [k] dst_release 1.89% [kernel] [k] __ip6_make_skb 1.87% [kernel] [k] __ip6_append_data 1.86% [kernel] [k] udpv6_sendmsg 1.86% [kernel] [k] ip6t_do_table 1.64% [kernel] [k] ipv6_dev_get_saddr 1.64% [kernel] [k] find_match 1.51% [kernel] [k] l3mdev_master_ifindex_rcu 1.24% [kernel] [k] ipv6_addr_label Eric Dumazet (6): ipv6: prepare RCU lookups for idev->addr_list ipv6: rcu conversion of ipv6_count_addresses() ipv6: ipv6_chk_custom_prefix() rcu conversion ipv6: ipv6_chk_prefix() rcu conversion ipv6: __ipv6_dev_get_saddr() rcu conversion ipv6: avoid cache line dirtying in ipv6_dev_get_saddr() net/ipv6/addrconf.c | 70 +++++++++++++++++++---------------------------------- 1 file changed, 25 insertions(+), 45 deletions(-) -- 2.14.2.920.gcf0c67979c-goog
