My router does indeed support it, but the set limit is far beyond what is should be even for 100 mbits ( 1879048192 ) by default. it has to be tuned to the link speed, to actually be effective considering the device driver has the code. I'm amazed how well it works and wondering why more drivers don't support this. It's the same principle as having a vehicle with "Eco-Boost" but never activating it.
that's the point of all these innovations, to USE them and have a happy medium. Relying on the pressure from a set bql without adjust the link speed is an awesome feature to reduce the tx queues while reducing latency. If only such a thing existed for the downstream and more devices supported bql.
So in your tests BQL is never really exercised, if you traffic shape below line-rate, the NIC bufffers (that BQL basically tries to keep at a reasonable length) never fill. And even without SQM in the mix the fact that your uplink is only 5 Mbps means that the NIC's queues should never grow excessively.
I gess I am missing something here (and I do endorse your message bql support would be much appreciated in the DOCSIS modem and in XDSL-modems).
In this test you should not see any effect of the BQL limits, as the bloated Buffers on the upstream leg of your link are probably inside your modem's DOCSIS section, which in all likelihood does not use bql.Now if you set your NIC to 10Mbps on a >=10 Mbps DOCSIS link, BQL will get exercised and might actually keep bufferbloat low even without a shaper like HTB or cake, but your downstream will now also be limited to 10Mbps...
So I agree that BQL is great, but it really really needs to be implemented inside the device at the near side of the real bottleneck link.
Observing the tx latency. My isp doesn't provide congestion control in any sense, so this new testing threw up some very different results. I've also test with flent on several occasions and even using stable on my r7000 with no changes and bql is not activated in that unit. Prior to BQL I could never achieve an A+ for bufferbloat unless I more than halved my download/upload bandwidth.