Function vm_page_advise

freebsd/vm/vm_page.c:4305–4345

* vm_page_advise * * Apply the specified advice to the given page. */

 * 	Apply the specified advice to the given page.
 */
void
vm_page_advise(vm_page_t m, int advice)
{

	VM_OBJECT_ASSERT_WLOCKED(m->object);
	vm_page_assert_xbusied(m);

	if (advice == MADV_FREE)
		/*
		 * Mark the page clean.  This will allow the page to be freed
		 * without first paging it out.  MADV_FREE pages are often
		 * quickly reused by malloc(3), so we do not do anything that
		 * would result in a page fault on a later access.
		 */
		vm_page_undirty(m);
	else if (advice != MADV_DONTNEED) {
		if (advice == MADV_WILLNEED)
			vm_page_activate(m);
		return;
	}

	if (advice != MADV_FREE && m->dirty == 0 && pmap_is_modified(m))
		vm_page_dirty(m);

	/*
	 * Clear any references to the page.  Otherwise, the page daemon will
	 * immediately reactivate the page.
	 */
	vm_page_aflag_clear(m, PGA_REFERENCED);

	/*
	 * Place clean pages near the head of the inactive queue rather than
	 * the tail, thus defeating the queue's LRU operation and ensuring that
	 * the page will be reused quickly.  Dirty pages not already in the
	 * laundry are moved there.
	 */
	if (m->dirty == 0)
		vm_page_deactivate_noreuse(m);
	else if (!vm_page_in_laundry(m))
		vm_page_launder(m);
}

/*
 *	vm_page_grab_release