Re: Making FFI callbacks call free() automatically when it's collected
- From: Mike Pall <mike-1207@xxxxxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Fri, 20 Jul 2012 16:07:13 +0200
Johnson Lin wrote:
> And there's a lot of callbacks I am allocating in the UI. At least
> dozens per menu. So when GC is not collecting for a while, it still
> hits the FFI callback limit in the LuaJIT.
You can raise the limit by changing LJ_NUM_CBPAGE in lj_def.h.
But this is only delaying the inevitable ...
[
The key problem always arises when there are different resources
with different scarcity with dependencies on each other. The GC
only reacts to memory pressure -- it doesn't even see the callback
slots. It sees the allocated function pointer objects, but they
take up only a couple of bytes each.
If you need a stable minimum of (say) 1 MB of memory after the
initial growth phase, then the GC will schedule its work to keep
the maximum memory below 2 MB. So if you try to allocate 1000
callback slots the GC will hardly take notice.
OTOH always scheduling a GC when the slots run out is a bad idea.
And the incremental GC would need to run at a pretty fast pace,
which makes it mostly non-incremental wrt. pause times.
]
IMHO scarce resources cannot easily be managed by a non-refcounting
GC -- it's not designed to do that. If you don't want to resort to
fully manual management, then RAII or other scope-based approaches
are your best bet.
--Mike
Other related posts:
