[PATCH v2 0/2] gro: optimise redundant parsing of packets

From: Richard Gobert
Date: Wed Feb 22 2023 - 09:59:57 EST


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 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.

In addition, the second commit contains a fix for a potential problem in BIG
TCP, which is detailed in the commit message itself.

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