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Re: Dom0 bad network performance (was: NetBSD/Xen samba performance low (compared to NetBSD/amd64))
Am 13.02.21 um 09:21 schrieb Jaromír Doleček:
Le sam. 13 févr. 2021 à 09:14, Matthias Petermann <mp%petermann-it.de@localhost> a écrit :
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 you try with NetBSD -current Xen kernel instead of 9.0?
There were some changes in xennet(4) there, which improved the performance.
I tried with both the following daily builds:
but unfortunately this kernels do panic. The device does not have a
serial console, so the only option I had was to film the boot sequence
and extract frames from it. Unfortunately, they are very blurry due to
the scrolling speed and I can only guess so much:
panic: kernel diagnostic assertion "!wskbd console initted" failed: file
"/home/source/ab/HEAD/src/sys/dev/wscons/wskbd.c". line 523
cpu0: Begin traceback...
Is this a known issue, or could another change (USB driver? XHCI?) be
playing into this?
However, I was able to convince the kernel to boot by forcing the use of
com1 as console in boot.cfg (although the interface does not exist). Now
any console output is missing, but network works and here are the test
results with 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 49112 connected to 192.168.2.50 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 61.3 MBytes 515 Mbits/sec 256 90.5 KBytes
[ 5] 1.00-2.00 sec 67.4 MBytes 565 Mbits/sec 334 73.5 KBytes
[ 5] 2.00-3.00 sec 65.9 MBytes 553 Mbits/sec 406 117 KBytes
[ 5] 3.00-4.00 sec 62.7 MBytes 526 Mbits/sec 313 84.8 KBytes
--> This is an improvement by a factor of 2 compared to 9.1 :-) I did
also test other window sizes. They did scale proportional to my tests
with 9.1 so I leave the results out here. I also repeated a test with my
"real" workload (sftp) and get an equivalent improvement here as well
(10 MByte/s instead of 5 MByte/s).
I think this is going in the right direction - just wondering what
factors influence the difference between Dom0 and the "pure" NetBSD that
might be worth another test.
Also, I also just read your 2nd mail - I also thought that xennet
normally should not have any impact on Dom0 performance. So it seems to
be more the "other changes" that help me in my case. Do you have a
suspicion which ones they could be? I'm particularly interested in
whether these can be easily backported to 9.1_STABLE if necessary?
Kind regards & many thanks
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