Comment by gpderetta
3 years ago
That's the lifetime of the objects in the arena, but wouldn't you recycle the arena itself across frames?
For requests it might make sense to have low and high water marks so that additional arenas are created during request peaks and destroyed after if you want to limit long term memory usage of your application.
Typically you would have different arenas for different lifetimes ('per frame', 'per level', 'per game session' - or maybe even more specialized, like the duration of an IO operation), and 'reset' the arenas at the end of their respective lifetimes (which is basically just setting the current 'top offset' to zero). This sort-of expects that object destruction is a no-op (e.g. no destructors need to be called).
The general idea being that you don't need to track granular 'per-object lifetimes', but only a handful of 'arena lifetimes', and all objects share the lifetime of the arena they've been allocated in.
Of course it's also possible to manually call a destructor on an object in the arena without recycling its memory, but I heavily prefer using plain POD structs without owning pointers and which can be safely 'abandondend' at any time without leaking memory.