netdev - Re: [RFC net-next 00/27] net and/or udp optimisations

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Date:   Wed, 6 Apr 2022 02:44:30 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     Pavel Begunkov <asml.silence@...il.com>
Cc:     netdev <netdev@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, Wei Liu <wei.liu@...nel.org>,
        Paul Durrant <paul@....org>
Subject: Re: [RFC net-next 00/27] net and/or udp optimisations

On Sun, Apr 3, 2022 at 6:08 AM Pavel Begunkov <asml.silence@...il.com> wrote:
>
> A mix of various net optimisations, which were mostly discovered during UDP
> testing. Benchmarked with an io_uring test using 16B UDP/IPv6 over dummy netdev:
> 2090K vs 2229K tx/s, +6.6%, or in a 4-8% range if not averaging across reboots.
>
> 1-3 removes extra atomics and barriers from sock_wfree() mainly benefitting UDP.
> 4-7 cleans up some zerocopy helpers
> 8-16 do inlining of ipv6 and generic net pathes
> 17 is a small nice performance improvement for TCP zerocopy
> 18-27 refactors UDP to shed some more overhead
>

Please send a smaller series first.

About inlining everything around, make sure to include performance
numbers only for the inline parts.
We can inline everything and make the kernel 4 x time bigger.
Synthetic benchmarks will still show improvements but in overall, we
add icache cost that is going to hurt latencies.
I vote that you focus on the other parts first.

Thank you.

> Pavel Begunkov (27):
>   sock: deduplicate ->sk_wmem_alloc check
>   sock: optimise sock_def_write_space send refcounting
>   sock: optimise sock_def_write_space barriers
>   skbuff: drop zero check from skb_zcopy_set
>   skbuff: drop null check from skb_zcopy
>   net: xen: set zc flags only when there is ubuf
>   skbuff: introduce skb_is_zcopy()
>   skbuff: optimise alloc_skb_with_frags()
>   net: inline sock_alloc_send_skb
>   net: inline part of skb_csum_hwoffload_help
>   net: inline skb_zerocopy_iter_dgram
>   ipv6: inline ip6_local_out()
>   ipv6: help __ip6_finish_output() inlining
>   ipv6: refactor ip6_finish_output2()
>   net: inline dev_queue_xmit()
>   ipv6: partially inline fl6_update_dst()
>   tcp: optimise skb_zerocopy_iter_stream()
>   net: optimise ipcm6 cookie init
>   udp/ipv6: refactor udpv6_sendmsg udplite checks
>   udp/ipv6: move pending section of udpv6_sendmsg
>   udp/ipv6: prioritise the ip6 path over ip4 checks
>   udp/ipv6: optimise udpv6_sendmsg() daddr checks
>   udp/ipv6: optimise out daddr reassignment
>   udp/ipv6: clean up udpv6_sendmsg's saddr init
>   ipv6: refactor opts push in __ip6_make_skb()
>   ipv6: improve opt-less __ip6_make_skb()
>   ipv6: clean up ip6_setup_cork
>
>  drivers/net/xen-netback/interface.c |   3 +-
>  include/linux/netdevice.h           |  27 ++++-
>  include/linux/skbuff.h              | 102 +++++++++++++-----
>  include/net/ipv6.h                  |  37 ++++---
>  include/net/sock.h                  |  10 +-
>  net/core/datagram.c                 |   2 -
>  net/core/datagram.h                 |  15 ---
>  net/core/dev.c                      |  28 ++---
>  net/core/skbuff.c                   |  59 ++++-------
>  net/core/sock.c                     |  50 +++++++--
>  net/ipv4/ip_output.c                |  10 +-
>  net/ipv4/tcp.c                      |   5 +-
>  net/ipv6/datagram.c                 |   4 +-
>  net/ipv6/exthdrs.c                  |  15 ++-
>  net/ipv6/ip6_output.c               |  88 ++++++++--------
>  net/ipv6/output_core.c              |  12 ---
>  net/ipv6/raw.c                      |   8 +-
>  net/ipv6/udp.c                      | 158 +++++++++++++---------------
>  net/l2tp/l2tp_ip6.c                 |   8 +-
>  19 files changed, 339 insertions(+), 302 deletions(-)
>  delete mode 100644 net/core/datagram.h
>
> --
> 2.35.1
>