Manpage of MINCORE

MINCORE

Section: Linux Programmer's Manual (2)
Updated: 2016-03-15
Index
 

NAME

mincore - determine whether pages are resident in memory  

SYNOPSIS

#include <unistd.h>
#include <sys/mman.h>

int mincore(void *addr, size_t length, unsigned char *vec);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

mincore():
    Since glibc 2.19:
        _DEFAULT_SOURCE
    Glibc 2.19 and earlier:
        _BSD_SOURCE || _SVID_SOURCE  

DESCRIPTION

mincore() returns a vector that indicates whether pages of the calling process's virtual memory are resident in core (RAM), and so will not cause a disk access (page fault) if referenced. The kernel returns residency information about the pages starting at the address addr, and continuing for lengthbytes.

The addrargument must be a multiple of the system page size. The lengthargument need not be a multiple of the page size, but since residency information is returned for whole pages, lengthis effectively rounded up to the next multiple of the page size. One may obtain the page size (PAGE_SIZE) using sysconf(_SC_PAGESIZE).

The vecargument must point to an array containing at least (length+PAGE_SIZE-1) / PAGE_SIZEbytes. On return, the least significant bit of each byte will be set if the corresponding page is currently resident in memory, and be clear otherwise. (The settings of the other bits in each byte are undefined; these bits are reserved for possible later use.) Of course the information returned in vecis only a snapshot: pages that are not locked in memory can come and go at any moment, and the contents of vecmay already be stale by the time this call returns.  

RETURN VALUE

On success, mincore() returns zero. On error, -1 is returned, and errnois set appropriately.  

ERRORS

EAGAINkernel is temporarily out of resources.
EFAULT
vecpoints to an invalid address.
EINVAL
addris not a multiple of the page size.
ENOMEM
lengthis greater than (TASK_SIZE - addr). (This could occur if a negative value is specified for length, since that value will be interpreted as a large unsigned integer.) In Linux 2.6.11 and earlier, the error EINVALwas returned for this condition.
ENOMEM
addrto addr+ lengthcontained unmapped memory.
 

VERSIONS

Available since Linux 2.3.99pre1 and glibc 2.2.  

CONFORMING TO

mincore() is not specified in POSIX.1, and it is not available on all UNIX implementations.  

BUGS

Before kernel 2.6.21, mincore() did not return correct information for MAP_PRIVATEmappings, or for nonlinear mappings (established using remap_file_pages(2)).  

SEE ALSO

mlock(2), mmap(2)


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
VERSIONS
CONFORMING TO
BUGS
SEE ALSO

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