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MINCORE(2) System Calls Manual MINCORE(2)


mincoredetermine residency of memory pages


Standard C Library (libc, -lc)


#include <sys/mman.h>

mincore(const void *addr, size_t len, char *vec);


The () 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>):

Page is in core (resident).
Page has been referenced by us.
Page has been modified by us.
Page has been referenced.
Page has been modified.
Page is part of a large (“super”) page.

The information returned by () may be out of date by the time the system call returns.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) 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.


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.


The mincore() system call will fail if:

The virtual address range specified by the addr and len arguments is not fully mapped.
The vec argument points to an illegal address.


madvise(2), mlock(2), mprotect(2), msync(2), munmap(2), getpagesize(3)


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

January 7, 2019 Debian