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Linux man pages : mincore (2)
MINCORE(2)		   Linux Programmer's Manual		    MINCORE(2)


mincore - get information on whether pages are in core


#include <unistd.h> #include <sys/mman.h> int mincore(void *start, size_t length, unsigned char *vec);


The mincore function requests a vector describing which pages of a file are in core and can be read without disk access. The kernel will supply data for length bytes following the start address. On return, the ker- nel will have filled vec with bytes, of which the least significant bit indicates if a page is core resident. For mincore to return successfully, start must lie on a page boundary. It is the caller's responsibility to round up to the nearest page. The length parameter need not be a multiple of the page size. The vector vec must be large enough to contain length/PAGE_SIZE bytes. One may obtain the page size from getpagesize(2).


On success, mincore returns zero. On error, -1 is returned, and errno is set appropriately.


EAGAIN kernel is temporarily out of resources EINVAL start is not a multiple of the page size, or len has a non-posi- tive value EFAULT vec points to an invalid address ENOMEM address to address + length contained unmapped memory, or memory not part of a file.


mincore should return a bit vector and not a byte vector. As of Linux 2.4.5, it is not possible to gain information on the core residency of pages which are not backed by a file. In other words, calling mincore on an region returned by an anonymous mmap(2) does not work and sets errno to ENOMEM. Unless pages are locked in memory, the contents of vec may be stale by the time they reach userspace.


mincore does not appear to be part of POSIX or the Single Unix Specifi- cation.


The mincore() function first appeared in 4.4BSD.


Since Linux 2.3.99pre1 and glibc 2.2.


getpagesize(2), mmap(2) Linux 2.4.5 2001-06-03 MINCORE(2)