Slow wired speed with sqm enabled wdr3600

Started playing with oldie wdr3600 installing on it openwrt 19.07 rc2. The device suffers from (quite) lower 2.4ghz speed compared with original fw, but 5ghz and wired speeds are all right. The problem arises when enabling SQM - the wireless connection sees small speed penalty (to be expected) but the wired connections download speed is slashed from 80 to 35 Mbps. This seems out of the ordinary.

iirc it could do a tad more back in the days.
but no, this seems about right.
it is a somewhat old and weak device.
its still useful as an low-end dumb_ap if you insist on keep using it but there are far better solutions available.

I don´t agree on that because the archer c7 devices does handle a lot more with enabled sqm and this SoCs are not much more powerful than the ar9344 chipset.

@uncleinf Can you provide some benchmarks (iperf) with the old ar71xx target and new ath79 for comparison?

Probably the new ath79 drivers does miss something like with the usb phy for ar934x chipsets...
I´ve created a PR that fixes the low USB speed on the new ath79 target:

can you share your sqm configuration?

config queue 'eth1'
option qdisc_advanced '0'
option linklayer 'none'
option interface 'eth0'
option debug_logging '0'
option upload '40000'
option qdisc 'cake'
option script 'piece_of_cake.qos'
option download '74000'
option enabled '1'
option verbosity '8'

I guess I should say that i have software offloading enabled, but with my testing this didnt make any difference - wired speeds with sqm is 50% of wireless 5ghz.

@juppin hmm i guess I could try, how do I switch targets?

Flashing from ar71xx to ath79 should work with a normal sysupgrade.
Flashing from ath79 to ar71xx with sysupgrade has to be forced with "-F".

For both cases it would be the best to not keep settings over a sysupgrade with "-n".

ath79 -> ar71xx: sysupgrade -F -n /path/to/sysupgrade.img
ar71xx -> ath79: sysupgrade -n /path/to/sysupgrade.img

I've found the problem, the wrong config is used when sqm is enabled:

  1. when connected over wifi - the download limit is download limit, the upload limit is upload limit - correct
  2. when connected over wired - the download limis is upload limit, the upload limit is upload limit - wrong.

I was getting half of the speed with sqm over wired because I had half of upload limit.

That is odd, could you post the output of:
cat /etc/config/sqm
tc -s qdisc
ifstatus wan
please. I assume that you connect to your upstream via the WAN port and your local wired traffic comes in via the LAN ports...

To elaborate, what I expect is that your router does not use plain eth0 as wan, but probably something eth0.2 for wan and eth0.1 for lan, instantiating the shaper on the base ethernet device simply has the side effects of inverting the directionality for either LAN or WAN. But that is just a hypothesis that might well be off.