Differential D8641 Diff 22532 head/lib/libc/sys/mmap.2

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head/lib/libc/sys/mmap.2

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	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT			.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY			.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF			.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	.\" SUCH DAMAGE.			.\" SUCH DAMAGE.
	.\"			.\"
	.\" @(#)mmap.2 8.4 (Berkeley) 5/11/95			.\" @(#)mmap.2 8.4 (Berkeley) 5/11/95
	.\" $FreeBSD$			.\" $FreeBSD$
	.\"			.\"
	.Dd February 18, 2015			.Dd November 25, 2016
	.Dt MMAP 2			.Dt MMAP 2
	.Os			.Os
	.Sh NAME			.Sh NAME
	.Nm mmap			.Nm mmap
	.Nd allocate memory, or map files or devices into memory			.Nd allocate memory, or map files or devices into memory
	.Sh LIBRARY			.Sh LIBRARY
	.Lb libc			.Lb libc
	.Sh SYNOPSIS			.Sh SYNOPSIS
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	Typically this prevents the update daemons from flushing pages dirtied			Typically this prevents the update daemons from flushing pages dirtied
	through such maps and thus allows efficient sharing of memory across			through such maps and thus allows efficient sharing of memory across
	unassociated processes using a file-backed shared memory map.			unassociated processes using a file-backed shared memory map.
	Without			Without
	this option any VM pages you dirty may be flushed to disk every so often			this option any VM pages you dirty may be flushed to disk every so often
	(every 30-60 seconds usually) which can create performance problems if you			(every 30-60 seconds usually) which can create performance problems if you
	do not need that to occur (such as when you are using shared file-backed			do not need that to occur (such as when you are using shared file-backed
	mmap regions for IPC purposes).			mmap regions for IPC purposes).
				Dirty data will be flushed automatically when all mappings of an object are
				removed and all descriptors referencing the object are closed.
	Note that VM/file system coherency is			Note that VM/file system coherency is
	maintained whether you use			maintained whether you use
	.Dv MAP_NOSYNC			.Dv MAP_NOSYNC
	or not.			or not.
	This option is not portable			This option is not portable
	across			across
	.Ux			.Ux
	platforms (yet), though some may implement the same behavior			platforms (yet), though some may implement the same behavior
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