---
name: "vm_page_alloc"
section: "9"
platform: "linux"
package: "freebsd-manpages"
version: "6.0-5"
release: "Debian 4.0 (Etch)"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/vm_page_alloc"
---

# vm\_page\_alloc(9)

allocate a page for a vm\_object

## 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 page\_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, but is not inserted into the pmap.

**vm\_page\_alloc**() will not block.

Its arguments are:

- *object*

  The VM object to allocate the page for.

- *pindex*

  The index into the object at which the page should be inserted.

- *page\_req*

  A flag indicating how the page should be allocated.

  - VM\_ALLOC\_NORMAL

    The page should be allocated with no special treatment.

  - VM\_ALLOC\_SYSTEM

    The page can be allocated if the cache queue is empty and the free page count is above the interrupt reserved water mark. If VM\_ALLOC\_INTERRUPT is set, the page can be allocated as long as the free page count is greater than zero. 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 and therefore the cache cannot be accessed. The page will only be returned successfully if the free count is greater than zero.

  - VM\_ALLOC\_ZERO

    Indicate a preference for a pre-zeroed page. There is no guarantee that the page thus returned will be zeroed, but it will be marked as such.

  - VM\_ALLOC\_NOOBJ

    The page is associated with an unmanaged memory region, that is, there is no backing VM object. This is typically used to allocate pages within the kernel virtual address space.

## 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⟩.