spends a fair
amount of time clearing objects, and this approach should probably be
revisited.
<P>
In most configurations, we use specialized sweep routines to handle common
small object sizes.  Since we allocate one mark bit per word, it becomes
easier to examine the relevant mark bits if the object size divides
the word length evenly.  We also suitably unroll the inner sweep loop
in each case.  (It is conceivable that profile-based procedure cloning
in the compiler could make this unnecessary and counterp