We're dealing with three linux systems:
a "server" (actually a workstation that is also used as desktop PC) running ubuntu 18.04.
an old client (laptop with sandy-bridge cpu, no dedicated GPU) running arch linux
a new client (laptop with comet lake cpu, dedicated Nvidia GPU, hybrid setting in the bios, no bumblebee installation) running debian testing and using the proprietary nvidia drivers from the debian repositories
the two clients are in the same network (adjacent ports on the switch, same IP range, both gigabit ethernet adapters, speedtest.net reports the same connection speed for both).
I can ssh onto the server from both clients and X forwarding generally works except much slower on the new client (as test cycle i start the intel vtune gui and close it once the main menu is completely drawn. that takes ~ 26s on the new client and ~5s on the old client).
ssh -vvv I don't see any difference between the two setups (both
firstname.lastname@example.org as cipher, neither use connection compression. in fact the
$HOME/.ssh/config files and
/etc/ssh/ssh_config files are the same (the latter shipped slightly differently but I copied the file from the old client to the new to rule out that that's where the difference comes from).
Obviously we would like to get x forwarding on the new client to get as fast as it is on the old client. suggestion where to look for differences? can the X configurations / graphics drivers on the clients cause the slowdown (we don't see general graphic issues on any of the three systems)?
Both systems run the same window manager (i3). enabling/disabling compression doesn't change the behaviour.
A bit by accident (though triggered by the suggestion of @symcbean) I noticed on the new client that the behaviour changes dramatically when switching network device on the new client: connecting through the USB-C to ethernet that came with it, I observe the slow behaviour. Connecting through wifi I get down to ~9s for the start-and-quit cycle mentioned above. (the old client uses the builtin ethernet adapter).
Digging further, while speedtest.net says both clients get 800Mbit/s (ethernet on both clients), a
scp from the server to the clients gets 90MB/s to the old client, but only 5 MB/s to the new client with ethernet (50MB/s with wifi).
ip addr I see the
qdisc setting differs between the clients:
- new client ethernet
<BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
- old client ethernet
<BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
- new client wifi
<BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
iperf3 (to a public iperf server)
[ ID] Interval Transfer Bitrate Retr Cwnd [ 5] 0.00-1.00 sec 92.7 MBytes 777 Mbits/sec 0 1.54 MBytes [ 5] 1.00-2.00 sec 73.8 MBytes 619 Mbits/sec 0 1.54 MBytes [ 5] 2.00-3.00 sec 71.2 MBytes 598 Mbits/sec 0 1.54 MBytes [ 5] 3.00-4.00 sec 76.2 MBytes 640 Mbits/sec 0 1.54 MBytes [ 5] 4.00-5.00 sec 97.5 MBytes 818 Mbits/sec 2 1.14 MBytes [ 5] 5.00-6.00 sec 95.0 MBytes 797 Mbits/sec 0 1.27 MBytes [ 5] 6.00-7.00 sec 93.8 MBytes 786 Mbits/sec 0 1.34 MBytes [ 5] 7.00-8.00 sec 93.8 MBytes 786 Mbits/sec 0 1.44 MBytes [ 5] 8.00-9.00 sec 95.0 MBytes 797 Mbits/sec 0 1.48 MBytes [ 5] 9.00-10.00 sec 86.2 MBytes 724 Mbits/sec 0 1.48 MBytes
new client (ethernet)
[ ID] Interval Transfer Bitrate Retr Cwnd [ 5] 0.00-1.00 sec 30.0 MBytes 252 Mbits/sec 49 382 KBytes [ 5] 1.00-2.00 sec 35.9 MBytes 301 Mbits/sec 0 447 KBytes [ 5] 2.00-3.00 sec 41.5 MBytes 348 Mbits/sec 0 515 KBytes [ 5] 3.00-4.00 sec 47.6 MBytes 399 Mbits/sec 0 580 KBytes [ 5] 4.00-5.00 sec 53.6 MBytes 450 Mbits/sec 0 648 KBytes [ 5] 5.00-6.00 sec 58.2 MBytes 489 Mbits/sec 0 714 KBytes [ 5] 6.00-7.00 sec 66.2 MBytes 555 Mbits/sec 0 781 KBytes [ 5] 7.00-8.00 sec 52.5 MBytes 440 Mbits/sec 10 625 KBytes [ 5] 8.00-9.00 sec 57.5 MBytes 482 Mbits/sec 0 690 KBytes [ 5] 9.00-10.00 sec 61.2 MBytes 513 Mbits/sec 0 740 KBytes