netdev - [RFC PATCH net-next 0/4] net: batched receive in GRO path

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Message-ID: <08c963dd-de14-7548-deb3-ec87570140a0@solarflare.com>
Date:   Thu, 30 Aug 2018 20:57:59 +0100
From:   Edward Cree <ecree@...arflare.com>
To:     <linux-net-drivers@...arflare.com>, <davem@...emloft.net>
CC:     <netdev@...r.kernel.org>
Subject: [RFC PATCH net-next 0/4] net: batched receive in GRO path

This series listifies part of GRO processing, in a manner which allows those
 packets which are not GROed (i.e. for which dev_gro_receive returns
 GRO_NORMAL) to be passed on to the listified regular receive path.
I have not listified dev_gro_receive() itself, or the per-protocol GRO
 callback, since GRO's need to hold packets on lists under napi->gro_hash
 makes keeping the packets on other lists awkward, and since the GRO control
 block state of held skbs can refer only to one 'new' skb at a time.
 Nonetheless the batching of the calling code yields some performance gains
 in the GRO case as well.

Herewith the performance figures obtained in a NetPerf TCP stream test (with
 four streams, and irqs bound to a single core):
net-next: 7.166 Gbit/s (sigma 0.435)
after #2: 7.715 Gbit/s (sigma 0.145) = datum + 7.7%
after #4: 7.890 Gbit/s (sigma 0.217) = datum + 10.1%
(Note that the 'net-next' results were distinctly bimodal, with two results
 of about 8 Gbit/s and the remaining ten around 7 Gbit/s.  I don't have a
 good explanation for this.)
And with GRO disabled through ethtool -K (thus simulating traffic which is
 not GRO-able but, being TCP, is still passed to the GRO entry point):
net-next: 4.756 Gbit/s (sigma 0.240)
after #4: 5.355 Gbit/s (sigma 0.232) = datum + 12.6%

Edward Cree (4):
  net: introduce list entry point for GRO
  sfc: use batched receive for GRO
  net: make listified RX functions return number of good packets
  net/core: handle GRO_NORMAL skbs as a list in napi_gro_receive_list

 drivers/net/ethernet/sfc/efx.c        |  11 +++-
 drivers/net/ethernet/sfc/net_driver.h |   1 +
 drivers/net/ethernet/sfc/rx.c         |  16 +++++-
 include/linux/netdevice.h             |   6 +-
 include/net/ip.h                      |   4 +-
 include/net/ipv6.h                    |   4 +-
 net/core/dev.c                        | 104 ++++++++++++++++++++++++++--------
 net/ipv4/ip_input.c                   |  39 ++++++++-----
 net/ipv6/ip6_input.c                  |  37 +++++++-----
 9 files changed, 157 insertions(+), 65 deletions(-)