The following observations can be made:

  * the heap gets more and more underutilized, although it seems to
    eventually stabilize somewhere around 5% (!) utilization (i.e.,
    total/alive = 20);

  * the "min yield" of the single-cell freelist grows way too fast as a
    reaction to the first memory allocation (at iteration 1000), which
    consequently leads to the increase of the total heap size.

Keep in mind that currently heap is never reclaimed, so its total size
can only increase.  Likewise, "min yield" can only increase, as its
typically a fraction (40% by default) of the total heap size.

Strangely enough, with 1.8, `alive-cell-heap' remains exactly constant
until iteration 1000.  I suspect something wrong with
`gc-live-object-stats' there...

Thanks,
Ludovic.