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FamPhetial
Contributor
Contributor

network performance on guest: READ much slower than WRITE

I have a  network problem between linux host and linux guest. Both running Arch Linux. The guest is using vmxnet3.

I see that the read speed (guest is receiver) is much less than the write speed. iperf3 on the guest shows this:

 

[  5]   0.00-10.00  sec  1.09 GBytes   936 Mbits/sec                  receiver
[  5]   0.00-10.00  sec  3.77 GBytes  3.24 Gbits/sec    0             sender

 

Full output:

# iperf3 -s
-----------------------------------------------------------
Server listening on 5201
-----------------------------------------------------------
Accepted connection from 192.168.132.37, port 49946
[ 5] local 192.168.132.57 port 5201 connected to 192.168.132.37 port 49948
[ ID] Interval Transfer Bitrate
[ 5] 0.00-1.00 sec 112 MBytes 937 Mbits/sec
[ 5] 1.00-2.00 sec 112 MBytes 941 Mbits/sec
[ 5] 2.00-3.00 sec 112 MBytes 941 Mbits/sec
[ 5] 3.00-4.00 sec 112 MBytes 941 Mbits/sec
[ 5] 4.00-5.00 sec 112 MBytes 941 Mbits/sec
[ 5] 5.00-6.00 sec 106 MBytes 892 Mbits/sec
[ 5] 6.00-7.00 sec 112 MBytes 941 Mbits/sec
[ 5] 7.00-8.00 sec 112 MBytes 942 Mbits/sec
[ 5] 8.00-9.00 sec 112 MBytes 941 Mbits/sec
[ 5] 9.00-10.00 sec 112 MBytes 941 Mbits/sec
[ 5] 10.00-10.00 sec 63.6 KBytes 486 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate
[ 5] 0.00-10.00 sec 1.09 GBytes 936 Mbits/sec receiver
-----------------------------------------------------------
Server listening on 5201
-----------------------------------------------------------
Accepted connection from 192.168.132.37, port 49950
[ 5] local 192.168.132.57 port 5201 connected to 192.168.132.37 port 49952
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 440 MBytes 3.68 Gbits/sec 0 327 KBytes
[ 5] 1.00-2.01 sec 375 MBytes 3.14 Gbits/sec 0 327 KBytes
[ 5] 2.01-3.01 sec 372 MBytes 3.12 Gbits/sec 0 327 KBytes
[ 5] 3.01-4.00 sec 372 MBytes 3.13 Gbits/sec 0 327 KBytes
[ 5] 4.00-5.01 sec 420 MBytes 3.52 Gbits/sec 0 327 KBytes
[ 5] 5.01-6.00 sec 376 MBytes 3.16 Gbits/sec 0 327 KBytes
[ 5] 6.00-7.00 sec 375 MBytes 3.15 Gbits/sec 0 327 KBytes
[ 5] 7.00-8.01 sec 379 MBytes 3.17 Gbits/sec 0 327 KBytes
[ 5] 8.01-9.00 sec 375 MBytes 3.16 Gbits/sec 0 327 KBytes
[ 5] 9.00-10.00 sec 374 MBytes 3.15 Gbits/sec 0 327 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-10.00 sec 3.77 GBytes 3.24 Gbits/sec 0 sender
-----------------------------------------------------------
Server listening on 5201

 

Why is that?

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FamPhetial
Contributor
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I guess I fexd it myself.

I had to create a second network adapter "host-only" with the guest using vmxnet3 on it as well. That solves the performance issue host/guest. I get 3+Gb/s now in both directions.

It is just weird that this is not working with the bridge interface. Looks like the bridge interface is using the physical NIC on the host as the bottleneck to communicate with the guest.

 

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