vm_page_reserve_pages() and vm_page_allocate_page() will now steal pages from
the inactive queue as needed.
* We currently never steal active pages anymore, but this might need to be
revised later (therefore, the page scanner never waits anymore, but uses
mutex_trylock() to lock a cache).
* The page scanner and writer now both run at normal priority - let's see how
that will work out.
* Introduced an inactive queue.
* Instead of shuffling pages around in the queue (and therefore destroying LRU)
the page stealing mechanism now uses a marker page to be able to release the
page lock without losing its position in the queue.
* The page writer now always grabs the whole release count of the semaphore, so
that there won't be a huge backlog to catch up with.
* vm_page_num_free_pages() now also includes the inactive queue as well as the
reserved pages (they are no longer regarded as free pages).
* Added a insert_page_after() function that inserts a page after another one,
needed by the marker code.
* clear_page() now gets a vm_page instead of a physical address which simplified
some code.
* Removed superfluous initialization of the queues (if those aren't zeroed on
start, we would have serious problems, anyway).
* Removed old and unimplemented dump_free_page_table() ("free_pages") KDL
command.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@22506 a95241bf-73f2-0310-859d-f6bbb57e9c96
f8941839c3