[Codel] [Bloat] The challenge

[Dave Taht]

On Wed, May 9, 2012 at 12:15 PM, Dave Taht <dave.taht at gmail.com> wrote:
> On Wed, May 9, 2012 at 12:10 PM, Roger Jørgensen <rogerj at gmail.com> wrote:
>> On Wed, May 9, 2012 at 7:16 AM, Simon Barber <simon at superduper.net> wrote:
>>> One question now remains - will codel AQM be sufficient on it's own in
>>> getting delays down to levels that users are happy with for the common
>>> latency sensitive interactive traffic - VoIP, gaming and Skype for example -
>>> or are the further reductions that can be had with traffic classification
>>> and smart queuing algorithms necessary? The nicest part about codel on it's
>>> own is that it works on opaque packets - it will handle VPNs and traffic
>>> within them nicely. It gets away from all the complexity required to
>>> classify traffic in a world where traffic is often trying to hide.
>>
>> I'm more worried about how long cascades of codel code in equipment
>> will work together, add lots of traffic to the mix, just how will it
>> behave then?
>
> Dunno. I look forward to finding out.
>
> I put up debian packages of the kernel for ubuntu 12.4 here:
>
> http://huchra.bufferbloat.net/~d/codel/linux/
>
> You'll need to build your own iproute2 from the current (v12) patch set.
>
> Basic tests are throttling down your network card to like 100Mbit and
> trying it, unless you have major cpu that can saturate gigE or higher.

Um, 'major' cpu is not required. (I spend too much time on relatively
lame embedded hardware.) Almost any box made in the last 5 years can
run at gigE+.

However, there are other reasons (like ease of packet captures, the
core targets of this being uplinks from consumer boxes running at
.1-20Mbit, etc., to run slower)

Seeing the scaling factors actually work is good, too. As a simple and
dramatic example, try running codel at 10Mbit, and compare it against
the default pfifo_fast.

ethtool -K eth0 TSO off
ethtool -K eth0 GSO off
ethtool -K eth0 UFO off
ethtool -s eth0 advertise 0x002 # 10Mbit. 0x008 100Mbit

some_bandwidth_test_or_tests

tc qdisc add dev eth0 root codel # optionally, add ecn

some_bandwidth_test_or_tests

>
> I'm mostly using netperf from svn head.
>
>>
>>
>> --
>>
>> Roger Jorgensen           | ROJO9-RIPE
>> rogerj at gmail.com          | - IPv6 is The Key!
>> http://www.jorgensen.no   | roger at jorgensen.no
>
>
>
> --
> Dave Täht
> SKYPE: davetaht
> US Tel: 1-239-829-5608
> http://www.bufferbloat.net



-- 
Dave Täht
SKYPE: davetaht
US Tel: 1-239-829-5608
http://www.bufferbloat.net