On 03/28 I updated 3 Debian testing systems on our LAN at home, the update including --
linux-image-4.15.0-2-amd64 Since that time two behavioral differences have been conspicuous on all three systems. The first is that these messages appear in dmesg during every boot process: [ 1.799465] platform regulatory.0: firmware: failed to load regulatory.db (-2) [ 1.799498] firmware_class: See https://wiki.debian.org/Firmware for information about missing firmware [ 1.799537] platform regulatory.0: Direct firmware load for regulatory.db failed with error -2 [ 1.799540] cfg80211: failed to load regulatory.db The second is that large file transfers on the LAN are almost unbelievably slow, requiring (for instance) more than three hours to copy a 5 gigabyte file from one system to another. Such operations required only a few minutes before the upgrade of 03/28. I found some information in threads at bbs.archlinux.org that indicated that this issue was supposed to be harmless, but I learned, also, that some systems have shown evidence of very slow file transfers following this kernel update. This apparently had something to do with a change in TCP congestion control to bbr. I ran the following command on all three systems: # sysctl net.ipv4.tcp_congestion_control=cubic File transfer speeds returned immediately to normal for all three systems. Naturally, this did nothing for the dmesg messages, but system backups and other file transfers no longer require ridiculous amounts of time. I saw nothing in the Debian bug tracker that seems to apply, but I may have been looking in the wrong places. I did fire up reportbug and tried to send the information to reportbug.debian.org, but got an SMMTP send failure. Would like to get the information in front of someone who might be interested and able to do something about it. Suggestions?
