[ovs-discuss] high cpu usage when use ovs

[shuangyang qian]

when i usage ovs for overlay network with geneve protocol, the topo is like
bellow.
two physic nodes, node1 and node2.
in node1 i have network namespace vm1, its ip is 192.168.100.10.
in node2 i have network namespace vm2, its ip is 192.168.100.20.
in vm1 i start iperf3 server, in vm2 i start iperf3 as client.
and get result is:
# iperf3 -c 192.168.100.10 -t 2
Connecting to host 172.20.0.4, port 5201
[  4] local 172.20.0.5 port 35272 connected to 172.20.0.4 port 5201
[ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
[  4]   0.00-1.00   sec   322 MBytes  2.70 Gbits/sec    0    231 KBytes

[  4]   1.00-2.00   sec   320 MBytes  2.68 Gbits/sec    2    237 KBytes

- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-2.00   sec   642 MBytes  2.69 Gbits/sec    2             sender
[  4]   0.00-2.00   sec   640 MBytes  2.68 Gbits/sec
 receiver

iperf Done.

as the physic network is 10G bw.

when i see the cpu usage in node1, i get the result is:
%Cpu18 :  0.7 us,  0.0 sy,  0.0 ni, 99.0 id,  0.3 wa,  0.0 hi,  0.0 si,
 0.0 st
%Cpu19 :  0.3 us,  0.0 sy,  0.0 ni, 99.7 id,  0.0 wa,  0.0 hi,  0.0 si,
 0.0 st
%Cpu20 :  0.0 us,  0.3 sy,  0.0 ni,  0.7 id,  0.0 wa,  0.0 hi, 99.0 si,
 0.0 st
%Cpu21 :  0.3 us, 22.1 sy,  0.0 ni, 52.9 id,  0.0 wa,  0.0 hi, 24.7 si,
 0.0 st
%Cpu22 :  0.3 us,  1.7 sy,  0.0 ni, 95.7 id,  0.0 wa,  0.0 hi,  2.3 si,
 0.0 st

as we can see, the 20s cpu has be full.
the thread of resource is:
  132 root      20   0       0      0      0 R  90.0  0.0   0:52.96
ksoftirqd/20

 9588 root      20   0    9756   2456   2212 S  51.8  0.0   7:59.99 iperf3

as we can see,  ksoftirqd/20 use 100% of the cpu.
i can not understand why  ksoftirqd/20 use the full of the cpu?
btw, i use the openvswitch.ko build from ovs tree of version 2.11.2.
in home dir of ovs tree:
# ll datapath/linux/openvswitch.ko
-rw-r--r-- 1 root root 14056752 Nov  7 11:26 datapath/linux/openvswitch.ko

anyone can give me some suggestions?
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