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Re: Dom0 bad network performance (was: NetBSD/Xen samba performance low (compared to NetBSD/amd64))



Hi Cherry,

Am 13.02.21 um 05:11 schrieb Mathew, Cherry G.:
Hi Matthias!

how big are your packet frames , and are the tests doing large numbers of parallel connections ?


as far as I know, iperf3 doesn't use parallel connections so my test is a single connection only.

The hint with the frames (I assume this is synonymous with the window size) was good. I actually get very different results here (all done with the NetBSD/Xen as Dom0):

1) 32K Window Size

mpeterma@nuc:~> iperf3 -w 32K -c 192.168.2.50
Connecting to host 192.168.2.50, port 5201
[  5] local 192.168.2.40 port 44520 connected to 192.168.2.50 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[ 5] 0.00-1.00 sec 20.7 MBytes 173 Mbits/sec 0 35.4 KBytes [ 5] 1.00-2.00 sec 21.1 MBytes 177 Mbits/sec 0 35.4 KBytes
[  5]   2.00-3.00   sec  21.1 MBytes   177 Mbits/sec    0   35.4 KBytes

2) 64K Window Size

mpeterma@nuc:~> iperf3 -w 64K -c 192.168.2.50
Connecting to host 192.168.2.50, port 5201
[  5] local 192.168.2.40 port 44388 connected to 192.168.2.50 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[ 5] 0.00-1.00 sec 25.3 MBytes 212 Mbits/sec 0 67.9 KBytes [ 5] 1.00-2.00 sec 24.9 MBytes 209 Mbits/sec 0 67.9 KBytes [ 5] 2.00-3.00 sec 25.2 MBytes 211 Mbits/sec 0 67.9 KBytes

3) 128K Window Size

mpeterma@nuc:~> iperf3 -w 128K -c 192.168.2.50
Connecting to host 192.168.2.50, port 5201
[  5] local 192.168.2.40 port 44464 connected to 192.168.2.50 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[ 5] 0.00-1.00 sec 31.5 MBytes 265 Mbits/sec 0 158 KBytes [ 5] 1.00-2.00 sec 31.7 MBytes 266 Mbits/sec 0 165 KBytes
[  5]   2.00-3.00   sec  31.9 MBytes   268 Mbits/sec    0    165 KBytes

4) 160K Window Size

mpeterma@nuc:~> iperf3 -w 160K -c 192.168.2.50
Connecting to host 192.168.2.50, port 5201
[  5] local 192.168.2.40 port 44560 connected to 192.168.2.50 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[ 5] 0.00-1.00 sec 31.6 MBytes 265 Mbits/sec 0 163 KBytes [ 5] 1.00-2.00 sec 31.7 MBytes 266 Mbits/sec 0 163 KBytes
[  5]   2.00-3.00   sec  31.8 MBytes   267 Mbits/sec    0    163 KBytes

5) 192K Window Size

mpeterma@nuc:~> iperf3 -w 192K -c 192.168.2.50
Connecting to host 192.168.2.50, port 5201
[  5] local 192.168.2.40 port 44492 connected to 192.168.2.50 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[ 5] 0.00-1.00 sec 32.5 MBytes 273 Mbits/sec 0 192 KBytes [ 5] 1.00-2.00 sec 32.3 MBytes 271 Mbits/sec 0 202 KBytes [ 5] 2.00-3.00 sec 32.1 MBytes 270 Mbits/sec 0 202 KBytes
[  5]   3.00-4.00   sec  31.9 MBytes   268 Mbits/sec   62    185 KBytes

It looks like the optimum in this case is a window size of 128K. As a comparison measurement, I also repeated the measurement with 128K again against the "pure" NetBSD kernel without Xen:

mpeterma@nuc:~> iperf3 -w 128K -c 192.168.2.50
Connecting to host 192.168.2.50, port 5201
[  5] local 192.168.2.40 port 44802 connected to 192.168.2.50 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[ 5] 0.00-1.00 sec 111 MBytes 932 Mbits/sec 4 130 KBytes [ 5] 1.00-2.00 sec 110 MBytes 922 Mbits/sec 27 164 KBytes
[  5]   2.00-3.00   sec   111 MBytes   930 Mbits/sec   50    194 KBytes

This means that with a window size of 128K the difference is even more significant, i.e. the speed under Xen is only a third of the speed achieved with a "pure" NetBSD kernel.

Can we already conclude something from this, or did I misunderstand the question about the packet frames?

Kind regards
Matthias



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