ned to the large object free list.
Each small object page is checked to see if all mark bits are clear.
If so, the entire page is returned to the large object free list.
Small object pages containing some reachable object are queued for later
sweeping, unless we determine that the page contains very little free
space, in which case it is not examined further.
<P>
This initial sweep pass touches only block headers, not
the blocks themselves.  Thus it does not require significant paging, even
if large section