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Man Pages


Manual Reference Pages  -  VM_PAGE_ALLOC (9)

NAME

vm_page_alloc - allocate a page for a
.Vt vm_object

CONTENTS

Synopsis
Description
Return Values
Notes
Authors

SYNOPSIS


.In sys/param.h
.In vm/vm.h
.In 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
.Vt 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
.An Chad David Aq davidc@acns.ab.ca .
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