* Reworked stealing pages: the page thief thread is gone now,

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

headers/private/kernel/vm_priv.h

@@ -49,6 +49,7 @@ status_t vm_page_fault(addr_t address, addr_t faultAddress, bool isWrite,
 	bool isUser, addr_t *newip);
 void vm_unreserve_memory(size_t bytes);
 status_t vm_try_reserve_memory(size_t bytes);
+void vm_schedule_page_scanner(uint32 target);
 status_t vm_daemon_init(void);
 
 const char *page_state_to_string(int state);