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>.

Debian                                            July 3, 2010                                  VM_PAGE_ALLOC(9)