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_NOBUSY
- The returned page will not be exclusive busy.
VM_ALLOC_NODUMP
- The returned page will not be included in any kernel core dumps
regardless of whether or not it is mapped in to KVA.
VM_ALLOC_NOOBJ
- Do not associate the allocated page with a vm object. The
object argument is ignored.
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.
VM_ALLOC_SBUSY
- The returned page will be shared busy.
VM_ALLOC_WIRED
- The returned page will be wired.
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.
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⟩.