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Eric Dumazet says: ==================== ipv6: ipv6_dev_get_saddr() rcu works 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 ==================== Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.