# [gclist] object aging rates in generational collectors

Nick Barnes Nick.Barnes@pobox.com
Fri, 05 Oct 2001 11:05:30 +0100

```One answer to this problem is dynamic arena sizing.  There's no reason
for each arena to have a fixed maximum size.

Nick Barnes
Ravenbrook Limited

At 2001-10-05 02:40:05+0000, "Ji-Yong D. Chung" writes:
>     This question is assumes that the generational collector
> uses BIBOP table and that arenas are equally partitioned.
>
>     The question is: doesn't different aging rates of
> different types of objects cause premature collection of ther
> types of objects?
>
> ====================================
>
>     Detailed Description of the question
>
>     If one has many arenas in each generation,
> [each arena corresponding to a memory pool for an
> object type], then rates of objects flowing through
> different generations, as they age, will be different
> for different arenas.
>
>     So, say you have 2 arenas, 1 for
> pairs, 1 for vectors.  If the rate of object creation
> and death is different for pairs and vectors, then
> the rate at which live pairs will flow through the generations
> will be different from the rate at which live vectors
> will move through the generations.
>
>     If the rate of flow (aging) is identical for all
> objects, then, when one performs garbage collection,
> all the arenas will be "cleaned up equally."
> If the rate of flow is not the same, the arena through
> which most number of objects move will need GC
> the most.  For other arenas, GC maybe premature.
>
>     In the worst case scenario, one small arena,
> which keeps accumulating objects, could trigger
> the GC of the whole heap, and thus GC of all
> other arenas which do not need GC.
>
>     Is there a solution to this "inefficiency"?
>
>     I speculate the solution would require careful sizing
> of arenas to account for different object birth/death
> rates for each arena.  Is there a way to determine
> this?
>
>

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