New Router Connection Speeds Redux
Apparently the iwlwifi driver is not so well designed.
The following change to
/etc/modprobe.d/iwlwifi.conf was the trick.
options iwlwifi 11n_disable=8
With that change I again tested iperf.
With 2.4 GHz:
From laptop to server: ~33 Mbps
From server to laptop: ~50 Mbps
With 5 GHz:
From laptop to server: ~61 Mbps
From server to laptop: ~95 Mbps
Before the change I was seeing ~45 Mbps from server to laptop using 5 GHz. The improvement is double.
Removing that iwlwifi option returns the system to the same dismal results.
Allegedly there is some kind of trade-off between “stability” and speed. Thus far I notice no packet drops or connectivity problems.
Interesting that I still see significant differences depending on which direction I run the iperf test. That is, at least on Ubuntu MATE. When I reboot into Slackware I see ~95 Mbps in both directions. Perhaps this is Yet Another Paper Cut in Ubuntu.
Thumping away at about 95 Mbps is better than what could be expected with 10/100 Mbps ethernet.
Too bad the developer does not want or won’t fix the problem in a more seamless manner. That is the world of free/libre software — something is always broken.