Bug#890343: linux: make fq_codel default for default_qdisc

[Noah Meyerhans <noahm@debian.org>]

On Fri, Feb 26, 2021 at 06:58:50PM +0100, Vincent Blut wrote:
> > > I think the distinction is that the other packages that tweak sysctl
> > > values don't claim to be doing so on behalf of the kernel team.  If
> > > the
> > > kernel team is responsible for the values being set, then the
> > > settings
> > > should come from a package that the kernel team owns, not some other
> > > package.
> > 
> > Right, maybe in linux-base?  Although that might annoy derivatives that
> > want different defaults.
> > 
> > procps is the wrong place, not just because it's out of our hands, but
> > because systemd applies sysctl configuration now and procps is
> > optional.
> 
> Is there a definitive answer from the kernel team about how this should be
> implemented? In the meantime, Noah sent [1].

I've rebased 
https://salsa.debian.org/kernel-team/linux/-/merge_requests/309 against
the current 'master' kernel branch on Salsa.  Basic test results are
below.  It'd be nice if the kernel team could have a look and give
feedback on the approach or recommend an alternative one if this isn't
the one they'd like to pursue.

# before reboot:
admin@ip-10-0-0-136:~$ /sbin/tc qdisc
qdisc noqueue 0: dev lo root refcnt 2
qdisc mq 0: dev ens5 root
qdisc pfifo_fast 0: dev ens5 parent :2 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
qdisc pfifo_fast 0: dev ens5 parent :1 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
admin@ip-10-0-0-136:~$ sudo apt install ./linux-image-5.16.0-rc3-cloud-amd64-unsigned_5.16~rc3-1~exp2_amd64.deb
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Note, selecting 'linux-image-5.16.0-rc3-cloud-amd64-unsigned' instead of './linux-image-5.16.0-rc3-cloud-amd64-unsigned_5.16~rc3-1~exp2_amd64.deb'
The following additional packages will be installed:
  firmware-linux-free
Suggested packages:
  linux-doc-5.16 debian-kernel-handbook grub-pc | grub-efi-amd64 | extlinux
The following NEW packages will be installed:
  firmware-linux-free linux-image-5.16.0-rc3-cloud-amd64-unsigned
...
admin@ip-10-0-0-136:~$ sudo reboot
Connection to 18.236.97.48 closed by remote host.
...
admin@ip-10-0-0-136:~$ uname -a
Linux ip-10-0-0-136 5.16.0-rc3-cloud-amd64 #1 SMP PREEMPT Debian 5.16~rc3-1~exp2 (2021-12-01) x86_64 GNU/Linux
admin@ip-10-0-0-136:~$ /sbin/tc qdisc
qdisc noqueue 0: dev lo root refcnt 2
qdisc mq 0: dev ens5 root
qdisc fq_codel 0: dev ens5 parent :2 limit 10240p flows 1024 quantum 1514 target 5ms interval 100ms memory_limit 32Mb ecn drop_batch 64
qdisc fq_codel 0: dev ens5 parent :1 limit 10240p flows 1024 quantum 1514 target 5ms interval 100ms memory_limit 32Mb ecn drop_batch 64