t sizes,
the collector normally does not directly allocate objects of every possible
request size.  Instead request are rounded up to one of a smaller number
of allocated sizes, for which free lists are maintained.  The exact
allocated sizes are computed on demand, but subject to the constraint
that they increase roughly in geometric progression.  Thus objects
requested early in the execution are likely to be allocated with exactly
the requested size, subject to alignment constraints.
See <TT>GC_init_size_m