[Cerowrt-devel] rebuilding my lab a bit, testing long rtts, testing pie, etc

Dave Taht dave.taht at gmail.com
Fri Jun 7 12:46:42 EDT 2013

Now that I'm done travelling...

 I've been building up my lab a bit to (as one example) do far more
complete netem delay and loss based testing of web and voip traffic under
load, in addition to the rrul work.

I am very interested as to suggestions as to what and how to evaluate
various loads. I've already added emulations of two of cisco's tests from
their pie paper, and have come up with a way to do the rest...

Currently I'm stuck: as the atom based motherboard I'd chosen has a totally
non-functional GM500 video chip in it. It does have decent e1000e ethernet
on board, and a slot where I stuck another e1000e based network card - and
I'm trying to create equivalent setups for cerowrt and the atom boxes for
comparison. I ran into all sorts of old problems like GRO offloads, etc,
but I'm gradually beating the bugs down while I look for another
cheap-but-good board to stack 4-6 of in the rack. (suggestions for a good
board to use welcomed. I also have some common hardware like raspberri pi,
beagleboard black, and smileplug on order, in addition to a couple android
devices, and a few new router candidates, all of which will start arriving
next week)

Anyway, there are some extremely early results up at:

on my conventional 20Mbit/4Mbit down/up model, complete with the ubuntu
13.4 kernel build and kernel patches I used, the shaper code is at
the debloat script to kill the offloads)

and now (darn it) I'm going back to trying to vacation in the hope some
more folk will take a look at the kernel, patches, etc, etc.


Pie code not thoroughly validated yet.


The current linux codel


The advanced ns2 codel model


(this shows that sfq's default buffer depth is too short at these RTTs and


fq_codel using ns2's model of codel

While validating the new hardware I also worked on some direct p2p stuff
between two machines at 10 and 100Mbit line rates:


I would be incredibly hesitant to draw any conclusions from any of the
above, much validation (with a fresh brain needed in my case) remains to be
done on the hardware and patches. I would welcome more eyeballs on the pie
patches in particular.

Dave Täht

Fixing bufferbloat with cerowrt:
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