|VM_PAGE_ALLOC(9)||FreeBSD Kernel Developer's Manual||VM_PAGE_ALLOC(9)|
NAMEvm_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_alloc( vm_object_t object, vm_pindex_t pindex, int req);
DESCRIPTIONThe 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:
- The VM object to allocate the page for. The object must be locked if VM_ALLOC_NOOBJ is not specified.
- The index into the object at which the page should be inserted.
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:
- The page should be allocated with no special treatment.
- 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_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:
- The returned page will not be exclusive busy.
- The returned page will not be included in any kernel core dumps regardless of whether or not it is mapped in to KVA.
- Do not associate the allocated page with a vm object. The object argument is ignored.
- Allocate the page only if it is cached. Otherwise, return NULL.
- 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.
- The returned page will be shared busy.
- The returned page will be wired.
- 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.
RETURN VALUESThe vm_page_t that was allocated is returned if successful; otherwise, NULL is returned.
NOTESThe pager process is always upgraded to VM_ALLOC_SYSTEM unless VM_ALLOC_INTERRUPT is set.
AUTHORSThis manual page was written by <firstname.lastname@example.org>.
|January 28, 2012||FreeBSD|