s of the heap are not in physical memory.
<P>
Nonempty small object pages are swept when an allocation attempt
encounters an empty free list for that object size and kind.
Pages for the correct size and kind are repeatedly swept until at
least one empty block is found.  Sweeping such a page involves
scanning the mark bit array in the page header, and building a free
list linked through the first words in the objects themselves.
This does involve touching the appropriate data page, but in most cases
it will 