SQM and cake in TurrisOS 5.2.7 - far lower speed than the link

Software SW help
1

I have an asymmetric FTTH connection (1gbit DL / 210 Mbit UL) with which I’ve been using cake and SQM with TurrisOS 3.x. An unfortunate problem of this connection is that there’s a double NAT (ISP device → DMZ on the Omnia): I’m saying this to put the matter into context for what follows.

My SQM configuration is:

config queue 'eth1'
        option interface 'eth1'
        option ingress_ecn 'ECN'
        option egress_ecn 'ECN'
        option itarget 'auto'
        option etarget 'auto'
        option linklayer 'none'
        option enabled '1'
        option download '950000'
        option upload '190000'
        option debug_logging '0'
        option verbosity '5'
        option qdisc 'cake'
        option script 'piece_of_cake.qos'
        option qdisc_advanced '1'
        option squash_dscp '1'
        option squash_ingress '1'
        option qdisc_really_really_advanced '1'
        option iqdisc_opts 'nat dual-dsthost'
        option eqdisc_opts 'nat dual-srchost'

However, when testing both with dlsreports and librespeed, there is a huge drop in DL speed if I enable SQM:

  • Without SQM: DL ~900Mbps, UL 210Mbps
  • With SQM: DL ~190Mbps~500Mbps, UL 190 Mbps

As far as I remember, this did not happen with TurrisOS 3.x (but I might’ve been misremembering things).

Is there something wrong in this configuration? Pinging the SQM expert @moeller0 here.