[Bloat] weird problem WRT1200 + CAKE on OpenWrt 18.06.2

[Toke Høiland-Jørgensen]

Mikael Abrahamsson <swmike at swm.pp.se> writes:

> Hi,
>
> I've been running openwrt 18.06.2 for a long time on my WRT1200AC, with 
> CAKE, and everything has been great. I always got A+ in dslreports for 
> bufferbloat. I have a 250/100 ETTH connection (IP over ethernet native, no 
> PPPoE, no PON).
>
> I noticed some intermittent network stuttering issues I wanted to diagnose 
> last week, so I started looking into this. When doing the test I get 
> +100ms spikes in the downstream direction when I run CAKE. If I instead 
> switch to FQ_CODEL I do not see these spikes. As a matter of fact, if I 
> set my downstream to 300 when running cake and let my ISP handle the 
> buffering then I get an average of 5-10ms worth of buffering with no 
> spikes. My ISP isn't bloated in that direction.

Hmm, this seems like it's an issue with the timers CAKE uses for
shaping. Not really sure why that would happen...

> # tc qdisc show dev eth1.2
> qdisc cake 801f: root refcnt 2 bandwidth 100Mbit diffserv3 triple-isolate nonat nowash no-ack-filter split-gso rtt 100.0ms noatm overhead 22
> qdisc ingress ffff: parent ffff:fff1 ----------------
>
> tc qdisc show dev ifb4eth1.2
> qdisc cake 8020: root refcnt 2 bandwidth 240Mbit diffserv3 triple-isolate nonat nowash no-ack-filter split-gso rtt 100.0ms noatm overhead 22

This looks like you're running sqm-scripts on a VLAN interface? Does it
make any difference if you run it on the physical eth1?

-Toke