fq_codel qdisc compiled but not enabled on 22.10

[Dave Taht]

fq_codel has been the default in ubuntu since #1436945

It is also now the default in debian. Somewhere between 22.04 and 22.10 though, it stopped being enabled by systemd? (it used to be enabled there via a sysctl), and thus 22.10 (I tried both ubuntu server and ubuntu studio) doesn't have it on. I rather *immediately* noticed this huge regression (I run my ethernet at 100Mbit, and thus immediately saw 400+ms latency) - and I hope it can be fixed in the next release?

it can also be made the default via compiling it into the kernel as a kernel default.

Aggh! death to fifos!

root@localhost:~# sysctl -a | grep qdisc
net.core.default_qdisc = pfifo_fast

disc pfifo_fast 0: dev eth0 parent :1 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
 Sent 5250 bytes 53 pkt (dropped 0, overlimits 0 requeues 0)
 backlog 0b 0p requeues 0

[Seth Arnold (seth-arnold)]

Very weird.

Oddly enough, there was a change in how the parameter was specified around systemd 248 -- but that change predates 22.04. The documentation suggests that it should just keep a service from failing in case the setting can't be set, so it feels like it shouldn't actually change anything here.

sarnold@wopr:/fst/trees/ubuntu/main/s/systemd $ grep -L -- 'net.core.default_qdisc = fq_codel' */sysctl.d/50-default.conf
systemd_204-5ubuntu20.31/sysctl.d/50-default.conf
systemd_204-5ubuntu20/sysctl.d/50-default.conf
sarnold@wopr:/fst/trees/ubuntu/main/s/systemd $ grep -- 'net.core.default_qdisc = fq_codel' */sysctl.d/50-default.conf
systemd_229-4ubuntu21.21/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_229-4ubuntu21.22/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_229-4ubuntu21.23/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_229-4ubuntu21.27/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_229-4ubuntu21.28/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_229-4ubuntu21.29/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_229-4ubuntu21.31/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_229-4ubuntu4/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.19/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.26/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.28/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.29/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.31/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.33/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.34/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.38/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.39/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.40/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.41/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.42/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.43/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.44/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.45/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.46/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.47/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.48/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.49/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.50/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.51/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.52/sysctl.d/50-default.conf:net.core.default_qdisc = fq_codel
systemd_237-3ubuntu10.53/sysctl.d/50-def...

[David Myers (demyers)]

I just got a Raspberry Pi 5 and after loading the Mantic image I noticed that the file /lib/sysctl.d/50-default.conf from systemd isn't present, causing the network interfaces to default to pfifo_fast.

This file is also missing from the build "ubuntu 24.04 LTS amd64 (daily) (20240210)" running as a VM under LXD.

I think this regression could be an unpleasant surprise for Jammy users when they migrate to Noble.

Thanks.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.