[Bloat] AQM and PPP on Linux

[Eric Dumazet]

On Tue, 2015-07-28 at 15:50 +0200, Juliusz Chroboczek wrote:
> > What distro are you on?
> 
> Debian.  (One machine stable, one testing.)
> 
> > There's a sysctl to set the default qdisc: net.core.default_qdisc.
> 
>     $ sysctl -a | grep default_qdisc
>     net.core.default_qdisc = pfifo_fast
> 
> > Set this to fq_codel and you should be good to go.
> 
> Is that safe?  I'm thinking lo and virtual interfaces.

Unless some user space script change it, virtual interfaces have
txqueuelen = 0, so no qdisc is set up on them

$ ifconfig lo | grep txqueuelen
          collisions:0 txqueuelen:0

$ tc -s -d qdisc sh dev lo
<empty>

So yes, this is reasonably safe to change net.core.default_qdisc