[Cake] dual-src/dsthost unfairness, only with bi-directional traffic

[Georgios Amanakis]

Thanks for testing Pete! I should note though, that patch is incorrect
in terms of triple-isolate. It can be further improved my
differentiating between srchost and dsthost. The results are the same
nevertheless. The same principle can also be applied to the sparse
flows.

However, I completely understand Jonathan when he says that this might
not be the optimal solution, and perhaps a different model of
flow-selection is necessary (e.g. doing exactly what the man page
says: first decide based on host priority, and then based on priority
among the flows of that host).

On Sat, Jan 26, 2019 at 2:35 AM Pete Heist <pete at heistp.net> wrote:
>
> I ran my original iperf3 test with and without the patch, through my one-armed router with hfsc+cake on egress each direction at 100Mbit:
>
> Unpatched:
>
> IP1 1-flow TCP up: 11.3
> IP2 8-flow TCP up: 90.1
> IP1 8-flow TCP down: 89.8
> IP2 1-flow TCP down: 11.3
> Jain’s fairness index, directional: 0.623 up, 0.631 down
> Jain’s fairness index, aggregate: 0.997
>
> Patched:
>
> IP1 1-flow TCP up: 51.0
> IP2 8-flow TCP up: 51.0
> IP1 8-flow TCP down: 50.7
> IP2 1-flow TCP down: 50.6
> Jain’s fairness index, directional: 1.0 up, 0.999 down
> Jain’s fairness index, aggregate: 0.999
>
> So this confirms George’s result. :)
>
> Obviously if we look at _aggregate_ fairness it’s essentially the same in both cases. I think directional fairness is what users would expect though.
>
> Can anyone think of any potentially pathological cases from considering only bulk flows for fairness, that I can test? Otherwise, I’d like to see this idea taken in...
>
> > On Jan 16, 2019, at 4:47 AM, gamanakis at gmail.com wrote:
> >
> > Of course I pasted the results for IP1 and IP2 the wrong way. Sorry!
> > These are the correct results, along with the *.flent.gz files.
> >
> > IP1:
> > flent -H 192.168.1.2 tcp_8down &
> > Data file written to ./tcp_8down-2019-01-15T223703.709305.flent.gz.
> > Summary of tcp_8down test run at 2019-01-16 03:37:03.709305:
> >
> >                             avg       median          # data pts
> > Ping (ms) ICMP   :         0.78         0.72 ms              342
> > TCP download avg :         6.03         5.83 Mbits/s         301
> > TCP download sum :        48.24        46.65 Mbits/s         301
> > TCP download::1  :         6.03         5.83 Mbits/s         298
> > TCP download::2  :         6.03         5.83 Mbits/s         297
> > TCP download::3  :         6.03         5.83 Mbits/s         297
> > TCP download::4  :         6.03         5.83 Mbits/s         298
> > TCP download::5  :         6.03         5.83 Mbits/s         298
> > TCP download::6  :         6.03         5.83 Mbits/s         298
> > TCP download::7  :         6.03         5.83 Mbits/s         297
> > TCP download::8  :         6.03         5.83 Mbits/s         298
> >
> >
> > flent -H 192.168.1.2 tcp_1up &
> > Data file written to ./tcp_1up-2019-01-15T223704.711193.flent.gz.
> > Summary of tcp_1up test run at 2019-01-16 03:37:04.711193:
> >
> >                           avg       median          # data pts
> > Ping (ms) ICMP :         0.79         0.73 ms              342
> > TCP upload     :        48.12        46.69 Mbits/s         294
> >
> >
> >
> > IP2:
> > flent -H 192.168.1.2 tcp_1down &
> > Data file written to ./tcp_1down-2019-01-15T223705.693550.flent.gz.
> > Summary of tcp_1down test run at 2019-01-16 03:37:05.693550:
> >
> >                           avg       median          # data pts
> > Ping (ms) ICMP :         0.77         0.69 ms              341
> > TCP download   :        48.10        46.65 Mbits/s         300
> >
> >
> > flent -H 192.168.1.2 tcp_8up &
> > Data file written to ./tcp_8up-2019-01-15T223706.706614.flent.gz.
> > Summary of tcp_8up test run at 2019-01-16 03:37:06.706614:
> >
> >                           avg       median          # data pts
> > Ping (ms) ICMP :         0.74         0.70 ms              341
> > TCP upload avg :         6.03         5.83 Mbits/s         301
> > TCP upload sum :        48.25        46.63 Mbits/s         301
> > TCP upload::1  :         6.04         5.86 Mbits/s         226
> > TCP upload::2  :         6.03         5.86 Mbits/s         226
> > TCP upload::3  :         6.03         5.86 Mbits/s         226
> > TCP upload::4  :         6.03         5.86 Mbits/s         225
> > TCP upload::5  :         6.03         5.86 Mbits/s         226
> > TCP upload::6  :         6.03         5.86 Mbits/s         226
> > TCP upload::7  :         6.03         5.78 Mbits/s         220
> > TCP upload::8  :         6.03         5.88 Mbits/s         277
> >
> >
> > <tcp_8up-2019-01-15T223706.706614.flent.gz><tcp_8down-2019-01-15T223703.709305.flent.gz><tcp_1up-2019-01-15T223704.711193.flent.gz><tcp_1down-2019-01-15T223705.693550.flent.gz>
>