bject(s)
in that page, the object kind, and the necessary mark bits for those
objects.  The size information can be used to map the candidate pointer
to the object starting address.  To accelerate this process, the page header
also contains a pointer to a precomputed map of page offsets to displacements
from the beginning of an object.  The use of this map avoids a
potentially slow integer remainder operation in computing the object
start address.
<LI>
The mark bit for the target object is checked and set. 