msync(2)							      msync(2)

NAME    [Toc]    [Back]

     msync - synchronize memory	with physical storage

SYNOPSIS    [Toc]    [Back]

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

     int msync(void *addr, size_t len, int flags);

DESCRIPTION    [Toc]    [Back]

     The function msync	writes all modified copies of pages over the range
     [addr, addr + len)	to their backing storage locations.  msync optionally
     invalidates any copies so that further references to the pages will be
     obtained by the system from their backing storage locations.  The backing
     storage for a modified MAP_SHARED mapping is the file the page is mapped
     to; the backing storage for a modified MAP_PRIVATE	mapping	is its swap
     area.

     flags is a	bit pattern built from the following values:

	  MS_ASYNC		   perform asynchronous	writes
	  MS_SYNC		   perform synchronous writes
	  MS_INVALIDATE		   invalidate mappings

     If	MS_ASYNC is set, msync returns immediately once	all write operations
     are scheduled; if MS_SYNC is set, msync does not return until all write
     operations	are completed.

     MS_INVALIDATE invalidates all cached copies of data in memory, so that
     further references	to the pages will be obtained by the system from their
     backing storage locations.

     msync will	fail if:

     [EINVAL]	    If addr is not a multiple of the page size as returned by
		    sysconf(3C).

     [EIO]	    An I/O error occurred while	reading	from or	writing	to the
		    file system.

     [ENOMEM]	    Addresses in the range (addr, addr + len) are outside the
		    valid range	for the	address	space of a process or pages
		    not	mapped are specified.

     [EBUSY]	    MS_INVALIDATE was specified	and one	or more	of the pages
		    was	locked in memory.

SEE ALSO    [Toc]    [Back]

     mmap(2), mpin(2), sysconf(3C).






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msync(2)							      msync(2)

DIAGNOSTICS    [Toc]    [Back]

     Upon successful completion, the function msync returns 0; otherwise, it
     returns -1	and sets errno to indicate the error.

NOTES    [Toc]    [Back]

     msync should be used by programs that require a memory object to be in a
     known state, for example, in building transaction facilities.


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