[Codel] BQL support in Ethernet drivers (and Kathie Nichols and Van Jacobson's new AQM, codel)

[Rick Jones]

On 05/21/2012 04:09 PM, Tobias Diedrich wrote:
> Rick Jones wrote:
>> On 05/21/2012 02:49 PM, Tobias Diedrich wrote:
>>> Rick Jones wrote:
>>>> On 05/20/2012 08:48 PM, Dave Taht wrote:
>>>>> Thx for the numbers!
>>>>>
>>>>> Could you do a TCP_RR while under load from UDP_STREAM?
>>>>
>>>> If you want to generate pretty pictures while doing so, you can
>>>> probably tweak
>>>> http://www.netperf.org/svn/netperf2/trunk/doc/examples/bloat.sh
>>>
>>> How about this:
>>> http://tdiedrich.de/~ranma/bufferbloat-rt3050/
>>
>> They look pretty I suppose, but it also looks like I've got the
>> vrules botched somehow.  Though I cannot find the bug just yet in
>> the repository copy.  The red vertical line should be at the start
>> of the UDP_STREAM test's results, and there should be a black one
>> right after.  They shouldn't be at the ends of the _RR test.  Did
>> you tweak that bit when you converted to a UDP_STREAM test?
>
> Ah, yes, I botched the vrules.
>
>> The other thing is it appears the scaling to make rrdtool look like
>> it supports dual y-axes could use a bit of tweaking.  I was pretty
>> much guessing there :(
>
> Well, I tweaked the scaling myself since I wasn't happy with the
> original result either. :)

I think my original ones had the unfortunate effect of putting lines on 
top of one another.  Your's seem to put them pretty far apart (at least 
sometimes).  We aught to be able to find some reasonable medium in there 
somewhere.  I'm thinking if latency is the metric of greatest interest, 
we want that to have the full y axis, and then the peak bandwidth of the 
STREAM test be about half-way up?

> I reuploaded new images with correct vrules and your scaling.
>
> Anything above 100Mbit can be assumed to be dropped here (although
> only the bridge seems to drop, the gige mac gets backpressure from
> the switch I think and just delays transmitting the next packet I
> suppose).
>
> I can do a TCP_STREAM test, but since the SoC lacks sufficient oomph
> to saturate a 100Mbit link the results are going to be boring I
> expect. I get about 3MiB/s, regardless of TCP_STREAM or TCP_SENDFILE.
> Maybe TCP_SENDFILE would be a bit faster if the driver implemented
> checksum offload.

I'm fine with folks using UDP_STREAM, so long as they are aware of the 
issues involved.

rick