I think you mean mem or cache, and there's a good chance it will remain in cache and not be flushed to ram for short lived objects.
> no one thinks that incrementing an integer is the slow part — destroying cache is.
agreed
Atomics are rarely needed as you should really try to avoid sharing ownership across threads and instead change your design to avoid that if you can.
> Only for atomics
I don't think cache coherency is aware of threads; they live at a level above it (IANAExpert though)
> where you use an atomic shared ptr to share across threads and then you downgrade it to a non atomic version in-thread (and can hand out another atomic copy at any time).
your idea of GC is very different from others', you are happy to do a ton of manual stuff. GC is generally about not doing a ton of manual stuff.