[Bloat] Getting started with sqm-scripts - latency good, bandwidth decimated

[Alan Jenkins]

On 19/01/2016, Brandon Applegate <brandon at burn.net> wrote:
> Disclaimer: if this is the wrong list for such a question - let me know.
> This is specifically about the sqm-scripts package...
>
> Hello,
>
> I’ve been reading all I can on the bufferbloat website and also trying to
> understand the evolution of the various scripts (debloat, sqm, etc).
>
> I managed to get sqm-scripts on my firewall (Ubuntu linux on a PC - no *wrt
> etc).  Got it built with the ‘linux’ platform.  Since this is Ubuntu 12.04 -
> I had to cheat a bit and pull down the iproute2 source from 14.04.  I’ve
> tweaked the main sqm script to reflect this for the tc bindary - this is
> working.  I also updated my kernel to a later version that supports
> fq_codel.
>
> My topology is ‘on a stick’.  I have one gig interface to a managed switch,
> on which are eth0.666 (outside/wan) and eth0.10 (inside).
>
> I have 30/5 cable service, and have tried both those values as well as 90%
> in my /etc/sqm/*conf file.
>
> I’ve tried both eth0 (raw/parent interface) as well as eth0.666.
>
> No matter what I do - my bandwidth is 10% of what it should be.  I get
> approx. 3/4mbit down + 2/3mbit up on dslreports speedtest.  Bufferbloat
> looks great though - A+.
>
> Is there something inherent I’m doing wrong ?  Something to do with my ‘on a
> stick’ topology biting me ?  Kernel version (Ubuntu’s 3.13.0-74-generic
> btw).
>
> Thanks in advance for any help or info (or pointer to a more appropriate
> list).

It doesn't sound like you're doing anything wrong :(.

I would make sure to check the rates on `tc class show dev eth0.666`
(and ifb4eth0.666).  Switching to `simplest.qos` could be easier to
debug.  With your simple.qos, there'll be several tracffic classes...
the `root` should be the specified `rate`, and it looks like all
classes save 1:11 should have a `ceil` just under the specified rate.

Not sure how to debug qos-scripts itself.  However the Gentoo wiki has
a 50-line script, which was corrected by dtaht :).  Like simplest.qos
this has a single class.
https://wiki.gentoo.org/wiki/Traffic_shaping

That would let you investigate the commands finely, as well as the
resulting state shown by `tc qdisc` and `tc class`, and really narrow
it down.

`dslreports.com` will show bandwidth and latency-under-load in each
direction independently, so you could work on a single direction.  I
would look at ingress only (the IFB) since that's where your bandwidth
decimation is so visible.  E.g. just comment out the egress section,
to avoid distractions.

I think you can run the htb without the fq_codel command at the end -
that is, it will default to a massive fifo, which will replace the
fq_codel in the output of `tc qdisc`, but to a first approximation it
will affect bandwidth.

Good luck
Alan