---
name: "mincore"
section: "2"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/mincore"
---

# mincore(2)

determine residency of memory pages

## NAME

**mincore** – determine residency of memory pages

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

**#include \<sys/mman.h\>**

*int*\

**mincore**(*const void \*addr*, *size\_t len*, *char \*vec*);

## DESCRIPTION

The **mincore**() system call determines whether each of the pages in the region beginning at *addr* and continuing for *len* bytes is resident or mapped, depending on the value of sysctl *vm.mincore\_mapped*. The status is returned in the *vec* array, one character per page. Each character is either 0 if the page is not resident, or a combination of the following flags (defined in ⟨sys/mman.h⟩):

- MINCORE\_INCORE

  Page is in core (resident).

- MINCORE\_REFERENCED

  Page has been referenced by us.

- MINCORE\_MODIFIED

  Page has been modified by us.

- MINCORE\_REFERENCED\_OTHER

  Page has been referenced.

- MINCORE\_MODIFIED\_OTHER

  Page has been modified.

- MINCORE\_PSIND(i)

  Page is part of a large (“super”) page with size given by index i in the array returned by [getpagesizes(3)](/getpagesizes/3.md).

- MINCORE\_SUPER

  A mask of the valid MINCORE\_PSIND() values. If any bits in this mask are set, the page is part of a large (“super”) page.

The information returned by **mincore**() may be out of date by the time the system call returns. The only way to ensure that a page is resident is to lock it into memory with the [mlock(2)](/mlock/2.md) system call.

If the *vm.mincore\_mapped* sysctl is set to a non-zero value (default), only the current process' mappings of the pages in the specified virtual address range are examined. This does not preclude the system from returning MINCORE\_REFERENCED\_OTHER and MINCORE\_MODIFIED\_OTHER statuses. Otherwise, if the sysctl value is zero, all resident pages backing the specified address range are examined, regardless of the mapping state.

## IMPLEMENTATION NOTES

Prior to the introduction of MINCORE\_PSIND() in FreeBSD 13.0, MINCORE\_SUPER consisted of a single bit equal to MINCORE\_PSIND(1). In particular, applications compiled using the old value of MINCORE\_SUPER will not identify large pages with size index 2 as being large pages.

## RETURN VALUES

The **mincore()** function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

## ERRORS

The **mincore**() system call will fail if:

- \[ENOMEM\]

  The virtual address range specified by the *addr* and *len* arguments is not fully mapped.

- \[EFAULT\]

  The *vec* argument points to an illegal address.

## SEE ALSO

[madvise(2)](/madvise/2.md), [mlock(2)](/mlock/2.md), [mprotect(2)](/mprotect/2.md), [msync(2)](/msync/2.md), [munmap(2)](/munmap/2.md), [getpagesize(3)](/getpagesize/3.md), [getpagesizes(3)](/getpagesizes/3.md)

## HISTORY

The **mincore**() system call first appeared in 4.4BSD.