I “live in Emacs”, like most of us (atleast at work). It has been getting slower release on release, async support doesn’t seem to have been picked up by most packages and native-comp has made it more brittle.
Over this time, we moved from running the OS on hardware to running in VMs, so fractional slowdown was expected. But what I have is a few X slower Emacs. I had never seen Emacs take a minute to indent a few thousand lines, for example. Maybe some modes have slower code.
BTW, I liked the idea on emacs-devel about PGO/FDO experiments. And, with a short PGO Emacs session and compiling Emacs with that profile, I see almost all the responsiveness issues disappear. What is left are slow indent-region and slow file opening, which seem unrelated to UI responsiveness.
Are there automated UI test runners? Just a matter of recording macros, or even writing out elisp, I guess. Having targeted tests and using them for PGO/FDO to do Emacs releases seems useful.