SQM limiting my broadband (internet with 600mbit/s download)

Hi All

I have cable internet with 600mbit/s download and 60mbit/s upload. I have installed SQM on my OpenWRT router which is version 19.07.4. OpenWRT router is connected to cable router which is transformed into bridge mode.

Here is my config of SQM:

I believe the config is right for my type of connection.

The problem is when SQM is off i get speed around 400mbit/s (sometimes more, sometimes less) which i am happy about:

However when I have SQM on it limits my download speed below 200mbit/s (usually around 170mbit/s):

Speed testing device is Linux with speedtest-cli package to test the speed. It is connected by wire to my OpenWRT Router. Router has Gigabit LAN interface, Linux device also. All cables are good quality CAT 6.

Do you know guys what might be the issue in my case?

your router is under resourced...

all tests ( which you should try to better control conditions and leverage alternate testing methods ) are subject to router core performance...


Your router might be running out of CPU cycles, traffic shaping is quite CPU intensive unfortunately.
I just added a section to the SQM FAQ trying to explain that in some detail. Let me know if that helps and what result you get in the top test on the router.


Thank you for your replies guys.

That would make sense.

My CPU is MT7621 which is dual core 880MHz and it has 512MB RAM. Would that be really not enough for SQM in my case?

Yes that chip is not enough CPU speed.

Without replacing the hardware, you could try running SQM only on the uplink. That is where most of the trouble occurs-- especially with asymmetric ISP speed.

SQM bandwidth should be set 5-10% lower than the measured wide-open speed. Measured wide-open speed should be consistent and close to the subscribed amount.


Thank you guys.

Do you know by any chance how fast has to be CPU to properly deal with SQM in case of lets say 1gbit link?

If you have 1 Gb link and want SQM or VPN, you pretty much need some multicore CPU based on either x86 or mvebu. Possibly also newer RaspberryPis' might do.

But old MIPS single-core devices are no-go.


Genuine 1 Gbit is pretty rare even nowadays. 2-3 years ago that would have been an utopistic dream. Most home routers have been designed for something like 100-300 Mbit/s combined download/upload bandwidth.


There are some success reports for the raspberry pi 4B, with an additional USB3 Gigabit ethernet dongle and an additional managed switch and/or AP (the Pi's wifi is not that useful, 2.4 GHz only). But that currently requires (snapshot) master builds, as the pi4b is not supported in stable 19.7 (and probably never will be, once OpenWrt 20 or 21 comes, the pi4b should be supported in stable then).