Almost a decade ago I was writing a desktop toolkit in Lua 5.1 and gdk/cairo bindings. Let’s say for fun, because it never seen the light in planned business. But it had animations and geometry dynamics (all soft, no hw accel). While GC seems to be fast and data/widget count was small, it suddenly froze every dozen of seconds for a substantial amount of time. First thing I tried was to trigger a [partial] collection after every event, but what happened was (I believe) incremental^ steps still accumulated into one big stop. Also I followed all critical paths and made allocations static-y. It got better, but never resolved completely. I didn’t investigate it further, and my hw was far from bleeding edge, thus no big conclusion. But since then I’ll think twice before doing something frametime-critical with GC. Each specific implementation requires a handful of wild tests at least before considering as an option in my book.
As others probably already mentioned, worst side of gc is that it is unpredictable and hard to be forced in a way that matches your specific pattern. With manual/raii mm you can make pauses predictable and non-accumulating collection debt and fit before “retrace” perfectly. Also simply relying on automatic storage in time critical paths is usually “can not” in gc envs.
^ if any, I can’t recall if 5.1 actually implemented true incremental gc back then
This is simply not the case. Its still just code after all. The problem was you were fighting the GC but that's just the symptom. The clear problem was leaking something every frame. With all the tooling these days its pretty easy to see exactly what is getting allocated and garbage collected so you know where to focus your efforts.
I started with C actually, but good ui is hard, and I decided to use Lua for a reason of not writing it all in C and hand-optimized style. I was forced to write ugly non-allocating code anyway, which defeated that idea completely. To focus your efforts, there must be a reason for these efforts in the first place.
But you must understand that lots of games are able to make this work. Call of Duty, for example, uses Lua for its UI scripting and is able to hit framerate. WoW uses Lua as well. Its not impossible or even impractical. There's plenty of reason to use a higher level language even if your core loops are hand optimized.
As others probably already mentioned, worst side of gc is that it is unpredictable and hard to be forced in a way that matches your specific pattern. With manual/raii mm you can make pauses predictable and non-accumulating collection debt and fit before “retrace” perfectly. Also simply relying on automatic storage in time critical paths is usually “can not” in gc envs.
^ if any, I can’t recall if 5.1 actually implemented true incremental gc back then