Back in the 2000's, someone wrote a game debugging tool in Squeak Smalltalk which ran concurrently with the game (written in C++) it was debugging. It "cheated" on its garbage collection by shutting GC off. At the end of each game loop tick, it was modified so it just disposed of all objects which weren't manually marked "to keep."
That sounds like the best way to do GC in a game. Another way is to use explicit memory pools, remember to allocate from the right pool, and throw it all out at once.
General GC is really overrated I think. Automatic retain counting is nicer because it's deterministic and you never have to scan memory. Compaction can be nice but you can live without it.
