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NAME

     vm_page_alloc — allocate a page for a vm_object

SYNOPSIS

     #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 req);

DESCRIPTION

     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, unless VM_ALLOC_NOOBJ is specified in the req.  The page may exist in the vm object
     cache, in which case it will be reactivated instead, moving from the cache into the object
     page list.

     vm_page_alloc() will not sleep.

     Its arguments are:

     object  The VM object to allocate the page for.  The object must be locked if VM_ALLOC_NOOBJ
             is not specified.

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

     req     The bitwise-inclusive OR of a class and any optional flags indicating how the page
             should be allocated.

             Exactly one of the following classes must be specified:

             VM_ALLOC_NORMAL     The page should be allocated with no special treatment.

             VM_ALLOC_SYSTEM     The page can be allocated if the cache is empty and the free
                                 page count is above the interrupt reserved water mark.  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.  A page
                                 will be returned successfully if the free page count is greater
                                 than zero.

             The optional flags are:

             VM_ALLOC_ZERO         Indicate a preference for a pre-zeroed page.  There is no
                                   guarantee that the returned page will be zeroed, but it will
                                   have the PG_ZERO flag set if it is zeroed.

             VM_ALLOC_NOOBJ        Do not associate the allocated page with a vm object.  The
                                   object argument is ignored.

             VM_ALLOC_NOBUSY       The returned page will not have the VPO_BUSY flag set.

             VM_ALLOC_WIRED        The returned page will be wired.

             VM_ALLOC_IFCACHED     Allocate the page only if it is cached.  Otherwise, return
                                   NULL.

             VM_ALLOC_IFNOTCACHED  Only allocate the page if it is not cached in the object.  If
                                   the page at the specified pindex is cached, NULL is returned
                                   instead.

RETURN VALUES

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

NOTES

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

AUTHORS

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