devel: consider fq_codel as the default qdisc for networking

[Andy Whitcroft]

This was raised on the kernel-team@ mailing list, we should look at this if other distros are starting to move.

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Date: Tue, 24 Mar 2015 10:54:37 -0700
From: Dave Taht <email address hidden>
To: Joseph Salisbury <email address hidden>
Cc: Kernel Team <email address hidden>, <email address hidden>
Subject: Re: Minutes from the Ubuntu Kernel Team meeting, 2015-03-24

I must confess I had hoped ubuntu would adopt fq_codel as the default
qdisc in this go-around. It is still not quite part of fedora´s
default either, but is now in arch, (and nearly everyone else
downstream from systemd), and has long been the default in openwrt,
and at this point, just requires a single sysctl to enable.

It certainly could use more widespread testing, perhaps in the next release?

d@nuc-client:~$ cat /etc/sysctl.d/10-bufferbloat.conf
net.core.default_qdisc=fq_codel

[Toke Høiland-Jørgensen (tohojo)]

Happy Arch user running with the fq_codel default for a while. I have also enabled it manually on the Ubuntu systems I administer (running 12.04 with the updated kernel packages, and 14.04). Will definitely second it being turned on by default!

[Conficio (kajkandler)]

Yes, lets fight #bufferbloat, especially for OS that goes into mobile devices (phone, tablet, laptop, netbook, internet audio player, TV, etc. which might connect to the network via WiFi and other wireless networks, as their speed might be different from the surrounding (home / small office) network. Because speed steps are the locations where bufferbloat piles up.

And lets keep a keen eye on Dave Taht's work on Wifi core as this will have another round of improvements to our mobile networked lives.

[Simon Iremonger (ubuntu-iremonger)]

From what I can see, updates in ubuntu have now fixed this, bionic system certainly seems to now be booting with /proc/sys/net/core/default_qdisc = fq_codel now!.

Can somebody confirm this and close this bug as 'fixed' ?

SECONDLY, Related bufferbloat-matter to make fq_codel work better to avoid packet-drops is outbound tcp ECN-enablement on ubuntu end-hosts -- please see related ubuntu bug #1773157 and mark/comment there please:-

https://bugs.launchpad.net/ubuntu/+source/procps/+bug/1773157

[Laurent Bonnaud (laurent-bonnaud)]

I also see fq_codel used as default:

# cat /proc/sys/net/core/default_qdisc
fq_codel

# ip addr
[...]
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000

[Simon Iremonger (ubuntu-iremonger)]

Interestingly, turns out that seemingly systemd is what is (currently) responsible for turning on fq_codel by default. See:-

https://github.com/systemd/systemd/commit/e6c253e363dee77ef7e5c5f44c4ca55cded3fd47

Be nice to then get that suggested into upstream linux as a default and/or procps for 'non-systemd' booting. Also see #1773157 -- ECN really needs to be properly enabled to give the best benefit for congestion with TCP streams present.

[Simon Iremonger (ubuntu-iremonger)]

Launchpad issue link didn't come out -- LP #1773157
https://bugs.launchpad.net/ubuntu/+source/procps/+bug/1773157

[Dave Taht (dave-taht)]

Just to point out here that fq_codel is not enabled properly in 22.10

https://bugs.launchpad.net/ubuntu/+bug/2003027