object' page queue under the single mutex lock.
First, all pages on the queue are prepared for free by calls to
vm_page_free_prep(), and pages which should not be returned to the
physical allocator (e.g. wired or fictitious) are simply removed from
the queue. On the second pass, vm_page_free_phys_pglist() inserts all
pages from the queue without relocking the mutex.
The change improves the object termination, e.g. on the process exit
where large anonymous memory objects otherwise cause relocks the free
queue mutex for each page. More, if several such processes are
exiting or execing in parallel, the mutex was highly contended on
the address space demolition.
Diagnosed and tested by: mjg (previous version)
Reviewed by: alc, markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
2fcd1ff68f