msync man page on SmartOS

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MSYNC(3C)							     MSYNC(3C)

       msync - synchronize memory with physical storage

       #include <sys/mman.h>

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

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

       The flags argument is a bit pattern built from the following values:

			perform asynchronous writes

			perform synchronous writes

			invalidate mappings

       If  flags  is  MS_ASYNC	or MS_SYNC, the function synchronizes the file
       contents to match the current contents of the memory region.

	   o	  All write references to the memory region made prior to  the
		  call are visible by subsequent read operations on the file.

	   o	  All writes to the same portion of the file prior to the call
		  may or may not be visible by read references to  the	memory

	   o	  Unmodified  pages  in the specified range are not written to
		  the underlying hardware.

       If flags is MS_ASYNC, the function  may	return	immediately  once  all
       write  operations are scheduled; if flags is MS_SYNC, the function does
       not return until all write operations are completed.

       If flags is MS_INVALIDATE, the function synchronizes  the  contents  of
       the memory region to match the current file contents.

	   o	  All  writes  to the mapped portion of the file made prior to
		  the call are visible by subsequent read  references  to  the
		  mapped memory region.

	   o	  All  write  references prior to the call, by any process, to
		  memory regions mapped to the same portion of the file	 using
		  MAP_SHARED, are visible by read references to the region.

       If  msync()  causes any write to the file, then the file's st_ctime and
       st_mtime fields are marked for update.

       Upon successful completion, msync() returns 0; otherwise, it returns −1
       and sets errno to indicate the error.

       The msync() function will fail if:

		 Some  or all of the addresses in the range [addr, addr + len)
		 are locked and MS_SYNC with the MS_INVALIDATE option is spec‐

		 Some  or  all	pages  in  the	range [addr,  addr +  len) are
		 locked for I/O.

		 The addr argument is not a multiple  of  the	page  size  as
		 returned by sysconf(3C).

		 The  flags  argument  is not some combination of MS_ASYNC and

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

		 Addresses  in	the  range  [addr, addr + len) are outside the
		 valid range for the address space of a	 process,  or  specify
		 one or more pages that are not mapped.

		 MS_INVALIDATE	was  specified and one or more of the pages is
		 locked in memory.

       The msync() function should be used by programs that require  a	memory
       object  to  be  in  a  known state, for example in building transaction

       Normal system activity can cause pages to be written to	disk.	There‐
       fore,  there  are  no  guarantees that msync() is the only control over
       when pages are or are not written to disk.

       See attributes(5) for descriptions of the following attributes:

       │Interface Stability │ Standard	      │
       │MT-Level	    │ MT-Safe	      │

       memcntl(2), mmap(2), sysconf(3C), attributes(5), standards(5)

				 Jul 24, 2002			     MSYNC(3C)

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