[PATCH v4 0/2] gro: optimise redundant parsing of packets

Richard Gobert
2023-03-20T16:43:15Z

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

By using the new ->transport_proto and ->network_proto fields, and also
storing the size of the network header, we can avoid parsing a second time
during the gro complete phase.

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.

Performance tests for TCP stream over IPv6 with extension headers
demonstrate rx improvement of ~0.7%.

For the benchmarks, I used 100Gbit NIC mlx5 single-core (power management
off), turboboost off.

Typical IPv6 traffic (zero extension headers):

for i in {1..5}; do netperf -t TCP_STREAM -H 2001:db8:2:2::2 -l 90 | tail -1; done
# before
131072 16384 16384 90.00 16391.20
131072 16384 16384 90.00 16403.50
131072 16384 16384 90.00 16403.30
131072 16384 16384 90.00 16397.84
131072 16384 16384 90.00 16398.00

# after
131072 16384 16384 90.00 16399.85
131072 16384 16384 90.00 16392.37
131072 16384 16384 90.00 16403.06
131072 16384 16384 90.00 16406.97
131072 16384 16384 90.00 16406.09

IPv6 over IPv6 traffic:

for i in {1..5}; do netperf -t TCP_STREAM -H 4001:db8:2:2::2 -l 90 | tail -1; done
# before
131072 16384 16384 90.00 14791.61
131072 16384 16384 90.00 14791.66
131072 16384 16384 90.00 14783.47
131072 16384 16384 90.00 14810.17
131072 16384 16384 90.00 14806.15

# after
131072 16384 16384 90.00 14793.49
131072 16384 16384 90.00 14816.10
131072 16384 16384 90.00 14818.41
131072 16384 16384 90.00 14780.35
131072 16384 16384 90.00 14800.48

IPv6 traffic with varying extension headers:

for i in {1..5}; do netperf -t TCP_STREAM -H 2001:db8:2:2::2 -l 90 | tail -1; done
# before
131072 16384 16384 90.00 14812.37
131072 16384 16384 90.00 14813.04
131072 16384 16384 90.00 14802.54
131072 16384 16384 90.00 14804.06
131072 16384 16384 90.00 14819.08

# after
131072 16384 16384 90.00 14927.11
131072 16384 16384 90.00 14910.45
131072 16384 16384 90.00 14917.36
131072 16384 16384 90.00 14916.53
131072 16384 16384 90.00 14928.88

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

include/net/gro.h | 33 ++++++++++++++++++++++++---------
net/core/gro.c | 18 +++++++++++-------
net/ethernet/eth.c | 14 +++++++++++---
net/ipv6/ip6_offload.c | 20 +++++++++++++++-----
4 files changed, 61 insertions(+), 24 deletions(-)

--
2.36.1