Homey performance improvement tricks with "many devices"?

Yes, big difference. Still C is much faster.
For example, finding a device ID in a sorted array with a binary search takes 5µs processor time (ok, just the inner loop). Also, I keep all processes running in a wait state. On every signal the process is forked and the task is executed. To keep forking (copy-on-write) fast, I use only a few KB of shared memory.
On a high-speed multi-core platform with a big heap, I would never consider these things. It would just complicate the programs and the performance gain would be negligible.
The only bottlenecks I have now are TCP/IP latency (100Mb/s on BB and wifi on Homey) and off course Homey itself.
By the way, did anyone ever ping Homey? My stats are ridicules:
Homey (wifi -57dBm): round-trip min/avg/max/stddev = 76.993/262.639/617.330/181.384 ms.
Beaglebone (wired): round-trip min/avg/max/stddev = 2.655/3.587/5.253/0.901 ms.
iPhone (wifi -60dBm): round-trip min/avg/max/stddev = 3.803/62.305/111.986/36.045 ms.
AppleTV (wired): round-trip min/avg/max/stddev = 2.667/3.781/4.593/0.685 ms.
All four were pinged from a laptop on wifi. Homey’s response time is horrible. On wifi I expect roundtrips of tens of ms, not hundreds.

I don’t blame Homey. It is just a matter of cause and effect. Changing the settings is exactly what I did and advise others to do as well.

Of course it depends on the type of module.
These settings stop a Dimmer2 from sending power figures:

And these settings limit the number of figures from a wall plug switch:

You need to tweak these settings until you receive just enough info for your use case. In my case, I just want to know if my coffee machine is off, idle, or brewing. When it is idle, the power usage fluctuates and that is what I largely filter out with these settings.

Sure, but not an option to consider for Athom. There’s simply not enough manpower to rewrite the current runtime in C.

This has always been an issue with Homey, mine also has pretty terrible stats. Sounds like a suboptimal WiFi-driver (it’s not related to ICMP, just uploading an app also is terribly slow compared to other devices in my network with similar hardware, like RPi’s).

Very interesting topic. Since v2 I have lost my interest in Homey due the bad performance. I also own quite a lot of devices.

Specially interesting the flows that do not get executed if Homey is too busy.

I’ll enable again my auto restart every night, look at that USB power thingy and start adding delays.

Does anyone has experience in upgrading to PRO with large amount of devices and whether it makes a difference. Because I feel nobody upgraded to PRO because of repairing each single device will take ages…

I did upgrade to pro and it seems to respond better and a bit faster. It is a lot of work to re-add all 30+ devices and fix all flows, like almost a day. There was no flow backup available at that time to make things more complicated.
So if it worth it to spend a 100 extra i’m not sure. You really have to ask yourself if you want to spend the time to copy everything to a new Homey. Perhaps it is a better idea to add another Homey to the first one and have it Work as slave controller. With this i mean not as a z-wave slave but divide stuff between the 2 homeys.