VM_PAGE_ALLOC(9) BSD 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_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 spec‐
ified 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 indi‐
cating 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 success‐
fully 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 speci‐
fied 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⟩.
BSD July 3, 2010 BSD
