netdev - kernel 4.15.0-rc9+ (net-next) high cpu load at 50Gbit/s

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Date:   Sat, 27 Jan 2018 23:23:34 +0100
From:   Paweł Staszewski <pstaszewski@...are.pl>
To:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: kernel 4.15.0-rc9+ (net-next) high cpu load at 50Gbit/s - about 6Mpps

Hi


Today I made some real life traffic tests with kernel 4.15.0-rc9

but when traffic reach 50Gbit/s and about 6Mpps cpou load rises fast 
from 48% to 100% for all cpu cores.

Here is some graph that presenting how cpu load rises when there was 
more pps.


https://ibb.co/mhD5ob


here is perf record from that time:

https://pastebin.com/3zqG1rvE


There is 8x 10G ixgbe 82599 interfaces teamed with teamd.

No traffic queueing - only pfifo fast on all interfaces.

No NAT or iptables forles other than INPUT (about 30rules)

All nic's have same ethtool settings:

ethtool -k eth0
Features for eth0:
Cannot get device udp-fragmentation-offload settings: Operation not 
supported
rx-checksumming: on
tx-checksumming: on
         tx-checksum-ipv4: off [fixed]
         tx-checksum-ip-generic: on
         tx-checksum-ipv6: off [fixed]
         tx-checksum-fcoe-crc: off [fixed]
         tx-checksum-sctp: on
scatter-gather: on
         tx-scatter-gather: on
         tx-scatter-gather-fraglist: off [fixed]
tcp-segmentation-offload: on
         tx-tcp-segmentation: on
         tx-tcp-ecn-segmentation: off [fixed]
         tx-tcp-mangleid-segmentation: off
         tx-tcp6-segmentation: on
udp-fragmentation-offload: off
generic-segmentation-offload: on
generic-receive-offload: on
large-receive-offload: off
rx-vlan-offload: on
tx-vlan-offload: on
ntuple-filters: on
receive-hashing: on
highdma: on [fixed]
rx-vlan-filter: on
vlan-challenged: off [fixed]
tx-lockless: off [fixed]
netns-local: off [fixed]
tx-gso-robust: off [fixed]
tx-fcoe-segmentation: off [fixed]
tx-gre-segmentation: on
tx-gre-csum-segmentation: on
tx-ipxip4-segmentation: on
tx-ipxip6-segmentation: on
tx-udp_tnl-segmentation: on
tx-udp_tnl-csum-segmentation: on
tx-gso-partial: on
tx-sctp-segmentation: off [fixed]
tx-esp-segmentation: off [fixed]
fcoe-mtu: off [fixed]
tx-nocache-copy: off
loopback: off [fixed]
rx-fcs: off [fixed]
rx-all: off
tx-vlan-stag-hw-insert: off [fixed]
rx-vlan-stag-hw-parse: off [fixed]
rx-vlan-stag-filter: off [fixed]
l2-fwd-offload: off
hw-tc-offload: off
esp-hw-offload: off [fixed]
esp-tx-csum-hw-offload: off [fixed]
rx-udp_tunnel-port-offload: on


ethtool -g eth0
Ring parameters for eth0:
Pre-set maximums:
RX:             4096
RX Mini:        0
RX Jumbo:       0
TX:             4096
Current hardware settings:
RX:             4096
RX Mini:        0
RX Jumbo:       0
TX:             2048


ethtool -c eth0
Coalesce parameters for eth0:
Adaptive RX: off  TX: off
stats-block-usecs: 0
sample-interval: 0
pkt-rate-low: 0
pkt-rate-high: 0

rx-usecs: 512
rx-frames: 0
rx-usecs-irq: 0
rx-frames-irq: 0

tx-usecs: 0
tx-frames: 0
tx-usecs-irq: 0
tx-frames-irq: 0

rx-usecs-low: 0
rx-frame-low: 0
tx-usecs-low: 0
tx-frame-low: 0

rx-usecs-high: 0
rx-frame-high: 0
tx-usecs-high: 0
tx-frame-high: 0