[pypy-dev] Pypy garbage collection

[Carl Friedrich Bolz]

On 17/03/14 20:04, Martin Koch wrote:
> Well, it would appear that we have the problem because we're generating
> a lot of garbage in the young generation, just like we're doing in the
> example we've been studying here.

No, I think it's because your generating a lot of garbage in the *old*
generation. Meaning objects which survive one minor collection but then
die.

> I'm unsure how we can avoid that in
> our real implementation. Can we force gc of the young generation? Either
> by gc.collect() or implcitly somehow (does the gc e.g. kick in across
> function calls?). 

That would make matters worse, because increasing the frequency of
minor collects means *more* objects get moved to the old generation
(where they cause problems). So indeed, maybe in your case making the
new generation bigger might help. This can be done using
PYPY_GC_NURSERY, I think (nursery is the space reserved for young
objects). The risk is that minor collections become unreasonably slow.

Anyway, if the example code you gave us also shows the problem I think
we should eventually look into it. It's not really fair to say "but
you're allocating too much!" to explain why the GC takes a lot of time.

Cheers,

Carl Friedrich