---
name: "vm_page_alloc"
section: "9freebsd"
platform: "linux"
package: "freebsd-manpages"
version: "12.2-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/vm_page_alloc/9freebsd"
---

# vm\_page\_alloc(9freebsd)

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 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*.

**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\_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*⟩.