[PATCH 0/2] gro: optimise redundant parsing of packets

[Richard Gobert <richardbgobert@gmail.com>]

Currently, the IPv6 extension headers are parsed twice: first in
ipv6_gro_receive, and then again in ipv6_gro_complete.

The field NAPI_GRO_CB(skb)->proto is used by GRO to hold the layer 4
protocol type that comes after the IPv6 layer. I noticed that it is set
in ipv6_gro_receive, but isn't used anywhere. By using this field, and
also storing the size of the network header, we can avoid parsing
extension headers a second time in ipv6_gro_complete.

The first commit frees up space in the GRO CB. The second commit reduces
the redundant parsing during the complete phase, using the freed CB
space.

I've applied this optimisation to all base protocols (IPv6, IPv4,
Ethernet). Then, I benchmarked this patch on my machine, using ftrace to
measure ipv6_gro_complete's performance, and there was an improvement.

Richard Gobert (2):
  gro: decrease size of CB
  gro: optimise redundant parsing of packets

 include/net/gro.h      | 32 +++++++++++++++++++++-----------
 net/core/gro.c         | 18 +++++++++++-------
 net/ethernet/eth.c     | 11 +++++++++--
 net/ipv4/af_inet.c     |  8 +++++++-
 net/ipv6/ip6_offload.c | 15 ++++++++++++---
 5 files changed, 60 insertions(+), 24 deletions(-)

-- 
2.36.1