Max,

I would put this text to a comment for clarity.

Feel free to ignore.

The reason of two consequent <collectgarbage> calls is not for "mark and
sweep" but rather for "full GC cycle + finalization of the resurrected
objects". The first call implements full (even 1.5) GC cycle; as a
result of this call some *objects* can be *released*, but the
corresponding *memory* is preserved in another list (gc->mmudata, IIRC)
to properly finalize the object (i.e. call __gc metamethod). Hence, the
second call finally releases the memory for the objects resurrected
within the sweep phase of the first call.

Since Max allocates plain FFI objects with no <ffi.gc> finalizers,
there is no need in the second <collectgarbage> call here.