pmap_page_exists_quick —
    determine if a page exists in a physical map
The
    pmap_page_exists_quick()
    function is used to quickly determine if the page m
    exists in the physical map pmap. It is typically
    called from the VM paging code.
The PV count used above may be changed upwards or downwards in
    future; it is only necessary that TRUE be returned
    for a small subset of pmaps for proper page aging.
The pmap_page_exists_quick() returns
    TRUE only if the PV entry for the physical map
    pmap is one of the first 16 PVs linked from the page
    m.
This manual page was written by Bruce M
    Simpson
    <bms@spc.org>.