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VM_PAGE_ALLOC(9)

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NAME    [Toc]    [Back]

     vm_page_alloc -- allocate a page for a vm_object

SYNOPSIS    [Toc]    [Back]

     #include <sys/param.h>
     #include <vm/vm.h>
     #include <vm/vm_page.h>

     vm_page_t
     vm_page_alloc(vm_object_t object, vm_pindex_t pindex, int page_req);

DESCRIPTION    [Toc]    [Back]

     The vm_page_alloc() function allocates a page at pindex within object.
     It is assumed that a page has not already been allocated at pindex.  The
     page returned is inserted into the object, but is not inserted into the
     pmap.

     vm_page_alloc() will not block.

     Its arguments are:

     object    The VM object to allocate the page for.

     pindex    The index into the object at which the page should be inserted.

     page_req  A flag indicating how the page should be allocated.

	       VM_ALLOC_NORMAL	   The page should be allocated with no special
 treatment.

	       VM_ALLOC_SYSTEM	   The page can be allocated if the cache
				   queue is empty and the free page count is
				   above the interrupt reserved water mark.
				   If VM_ALLOC_INTERRUPT is set, the page can
				   be allocated as long as the free page count
				   is greater than zero.  This flag should be
				   used only when the system really needs the
				   page.

	       VM_ALLOC_INTERRUPT  vm_page_alloc() is being called during an
				   interrupt and therefore the cache cannot be
				   accessed.  The page will only be returned
				   successfully if the free count is greater
				   than zero.

	       VM_ALLOC_ZERO	   Indicate a preference for a pre-zeroed
				   page.  There is no guarantee that the page
				   thus returned will be zeroed, but it will
				   be marked as such.

	       VM_ALLOC_NOOBJ	   The page is associated with an unmanaged
				   memory region, that is, there is no backing
				   VM object.  This is typically used to allocate
 pages within the kernel virtual
				   address space.

RETURN VALUES    [Toc]    [Back]

     The vm_page_t that was allocated is returned if successful; otherwise,
     NULL is returned.

NOTES    [Toc]    [Back]

     The pager process is always upgraded to VM_ALLOC_SYSTEM unless
     VM_ALLOC_INTERRUPT is set.

AUTHORS    [Toc]    [Back]

     This man page was written by Chad David <davidc@acns.ab.ca>.


FreeBSD 5.2.1			 July 13, 2001			 FreeBSD 5.2.1
[ Back ]
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