问题
I am confused to see huge difference between netcat and iperf results. I am having 10 G link connecting my server and client. I am getting around 10Gb/s for iperf but only ~280 MB/s for netcat. What can be the error ?
For Iperf
Server
iperf -s
Client
iperf -c 172.79.56.27 -i1 -t 10
Result:
Client connecting to 172.79.56.27, TCP port 5001
TCP window size: 85.0 KByte (default)
------------------------------------------------------------
[ 3] local 172.79.56.28 port 46058 connected with 172.79.56.27 port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0- 1.0 sec 1.07 GBytes 9.23 Gbits/sec
[ 3] 1.0- 2.0 sec 1.09 GBytes 9.35 Gbits/sec
[ 3] 2.0- 3.0 sec 1.09 GBytes 9.35 Gbits/sec
[ 3] 3.0- 4.0 sec 1.09 GBytes 9.35 Gbits/sec
[ 3] 4.0- 5.0 sec 1.09 GBytes 9.36 Gbits/sec
[ 3] 5.0- 6.0 sec 1.09 GBytes 9.35 Gbits/sec
[ 3] 6.0- 7.0 sec 1.09 GBytes 9.36 Gbits/sec
[ 3] 7.0- 8.0 sec 1.09 GBytes 9.35 Gbits/sec
[ 3] 8.0- 9.0 sec 1.09 GBytes 9.36 Gbits/sec
[ 3] 9.0-10.0 sec 1.09 GBytes 9.35 Gbits/sec
[ 3] 0.0-10.0 sec 10.9 GBytes 9.34 Gbits/sec
For netcat,
Server
nc -v -v -l -n 2222 >/dev/null
Client
time dd if=/dev/zero | nc -v -v -n 172.79.56.27 2222
Connection to 172.79.56.27 2222 port [tcp/*] succeeded!
^C6454690+0 records in
6454690+0 records out
3304801280 bytes (3.3 GB) copied, 11.4463 s, 289 MB/s
real 0m11.449s
user 0m6.868s
sys 0m15.372s
回答1:
Mr user1352179,
Run your netcat test again and watch htop in another window. I bet you will see that the bottleneck here is the single thread of dd reading /dev/zero. Try running the test again in parallel with 'n' instances of dd|netcat where 'n' = the # of cores in your system. Then add the total bandwidth together from all parallel runs to see the real result. (Make sure you transmit on different ports & have your receiving end running multiple threads as well & listening on multiple ports).
来源：https://stackoverflow.com/questions/26135369/huge-difference-in-netcat-and-iperf-results-for-a-10g-link