Cake Latency Target

Is there any way to force Cake to accept numbers above 5% of the calculated rtt? I'm trying to set this to 20ms with no luck.
sqm.eth1=queue
sqm.eth1.verbosity='5'
sqm.eth1.debug_logging='0'
sqm.eth1.interface='eth0.2'
sqm.eth1.qdisc_advanced='1'
sqm.eth1.squash_dscp='1'
sqm.eth1.squash_ingress='1'
sqm.eth1.ingress_ecn='ECN'
sqm.eth1.linklayer='ethernet'
sqm.eth1.linklayer_advanced='1'
sqm.eth1.tcMTU='2047'
sqm.eth1.tcTSIZE='128'
sqm.eth1.qdisc='cake'
sqm.eth1.script='piece_of_cake.qos'
sqm.eth1.overhead='18'
sqm.eth1.tcMPU='0'
sqm.eth1.linklayer_adaptation_mechanism='cake'
sqm.eth1.qdisc_really_really_advanced='1'
sqm.eth1.egress_ecn='ECN'
sqm.eth1.download='56100'
sqm.eth1.upload='4930'
sqm.eth1.enabled='1'
sqm.eth1.itarget='7.5ms' <<<<<----------???
sqm.eth1.etarget='7.5ms' <<<<<---------???
sqm.eth1.iqdisc_opts='rtt 150ms nat dual-dsthost mpu 64'
sqm.eth1.eqdisc_opts='rtt 150ms nat dual-srchost mpu 64'

No, cake does not offer that; that said you could always compile your own cake module and change the target, but IIRC cake will adjust the target if the bandwidth gets to low, basically to always allow at least one MTU sized packet in the queue. But why do you want to manipulate target? The theory behind the 5% set-point for target seems quite sane...

Cake SQM with RTT 100ms

Cake SQM with RTT 150ms

I'm attempting to control the intermittent latency spikes to the absolute minimum. Docsis is a brutal beast on latency.

Which intermittent latency spikes? IN my eyes bot RRUL results look pretty decent. Maybe if you manually set the latency y-axis to a range of 0 to 100 there are visible spikes, but the averages look pretty decent.
Please note that the RTT/interval parameter basically defines the time window in which fq_codel/cake expect the sender to react to the signaling, typically this should be roughly in the order of magnitude of the RTT (aim rather a bit above the typical unloaded RTT than below), 100ms works pretty well for typical internet usage, assuming your servers are on the same continent as you are. If your game servers are only say 40ms RTT away, you should configure cake accordingly (note that this will lead to some bandwidth sacrifices for flows with a longer RTT). The target value is theoretically deduced to be optimally at 5-10% of the RTT (see https://tools.ietf.org/html/draft-ietf-aqm-codel-07#section-5.2 for the rationale).
That said if you really really want to play with target, fq_codel does allow to manually set the target and luci-app-sqm actually exposes those values, but note again short of extending target to allow at least a full MTU worth of packets at the given bandwidth playing with target is probably barking up the wrong tree...

Thanks for the insight, learning more and more each day reading through the mailing lists and of course the lede documentation . Suppose I was reading those plots wrong, it was hectic the other day :grin: