Try it without plugins, see if you get the same issue. If not, then add plugins one by one to see if any cause the issue, or if it is aggregate of all the plugins, and especially the GUIs of said plugins (Might not matter if the GUI is not visible).
Or try your plug-ins without ardour… (Seriously though, I would be surprised if it was a plug-in issue, even though we plug-in devs may be responsible for most of the evils of the world… allegedly… unless its just a particularly CPU heavy session generally, and ardour is CPU, rather than GPU bound as a result).
i use same plugins in both Bitwig, Renoise, Ardour, Mixbus, and while it is known that TDR plugins are hard on resources - they do not cause noticeable fps drop in DAW unless DSP is almost reaching max
Mike you of all people should know by now that I am not out to blame plugin manufacturers. The point of my (brief, as I was on a phone) suggestion was to try to figure out if it WAS a plugin issue. If the issue disappears when plugins are not used then looking at that plugin, still doesn’t mean that it is the plugin itself, but yes that makes it more likely.
I honestly wasn’t expecting a single plugin to cause a huge issue there. That being said I have had issues with particular plugins on M1 that I have used in Ardour and other hosts as well, that cause a significant performance drop even with lower DSP usage (And equivalents when discussing other hosts), that used to not cause that issue before running on ARM. I haven’t always had time to investigate thoroughly why it is that was happening but it was happening on more hosts than just Ardour/Mixbus, and not all hosts.
And by the way, I haven’t seen similar issues myself. I have had students have issues, but every time I look at their computers when they see such issues, they are running lots of other programs that are known to cause system wide slowdowns, like Zoom, Chrome with lots of tabs, or even Spotify. Having them close those programs always makes a difference in their performance.
All that being said I would be surprised if that was the case here, and instead I do suspect (Without much proof) an issue with how graphics are drawn, possibly with GTK not supporting Metal but it could also be with plugin UIs and the previous discussions about closing plugin UI behavior on Ardour/Mixbus, (Which for the record we should not dredge up again the entire discussion, other than to determine if that might be part of a cause… which again my suggestion to try without plugins).
Yes that occurred to me too after my initial post - Its been a while since I’ve done much Mac development, and not on recent Apple Silicon / ARM powered Macs, but my suspicion (without any proof) would likely be something in the guts of GTK itself rather than specifically Ardour. Ardour would not be the only application to have run into issues with cross-platform UI toolkits ported to macOS