[Midnightbsd-cvs] src [10293] trunk/share/man/man5/tmpfs.5: update tmpfs.5

[laffer1 at midnightbsd.org]

Revision: 10293
          http://svnweb.midnightbsd.org/src/?rev=10293
Author:   laffer1
Date:     2018-06-03 12:58:26 -0400 (Sun, 03 Jun 2018)
Log Message:
-----------
update tmpfs.5

Modified Paths:
--------------
    trunk/share/man/man5/tmpfs.5

Property Changed:
----------------
    trunk/share/man/man5/tmpfs.5

Modified: trunk/share/man/man5/tmpfs.5
===================================================================
--- trunk/share/man/man5/tmpfs.5	2018-06-03 16:57:22 UTC (rev 10292)
+++ trunk/share/man/man5/tmpfs.5	2018-06-03 16:58:26 UTC (rev 10293)
@@ -1,7 +1,13 @@
+.\" $MidnightBSD$
 .\"-
 .\" Copyright (c) 2007 Xin LI
+.\" Copyright (c) 2017 The FreeBSD Foundation, Inc.
 .\" All rights reserved.
 .\"
+.\" Part of this documentation was written by
+.\" Konstantin Belousov <kib at FreeBSD.org> under sponsorship
+.\" from the FreeBSD Foundation.
+.\"
 .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions
 .\" are met:
@@ -47,14 +53,14 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.\" $MidnightBSD$
+.\" $FreeBSD: stable/10/share/man/man5/tmpfs.5 316237 2017-03-30 05:57:44Z ngie $
 .\"
-.Dd April 23, 2012
+.Dd January 20, 2017
 .Dt TMPFS 5
 .Os
 .Sh NAME
 .Nm tmpfs
-.Nd "efficient memory file system"
+.Nd "in-memory file system"
 .Sh SYNOPSIS
 To compile this driver into the kernel,
 place the following line in your
@@ -72,17 +78,40 @@
 .Sh DESCRIPTION
 The
 .Nm
-driver will permit the
-.Fx
-kernel to access
+driver implements an in-memory, or
 .Tn tmpfs
-file systems.
+file system.
+The filesystem stores both file metadata and data in main memory.
+This allows very fast and low latency accesses to the data.
+The data is volatile.
+An umount or system reboot invalidates it.
+These properties make the filesystem's mounts suitable for fast
+scratch storage, like
+.Pa /tmp .
+.Pp
+If the system becomes low on memory and swap is configured (see
+.Xr swapon 8 ),
+the system can transfer file data to swap space, freeing memory
+for other needs.
+Metadata, including the directory content, is never swapped out by the
+current implementation.
+Keep this in mind when planning the mount limits, especially when expecting
+to place many small files on a tmpfs mount.
+.Pp
+When
+.Xr mmap 2
+is used on a file from a tmpfs mount, the swap VM object managing the
+file pages is used to implement mapping and avoid double-copying of
+the file data.
+This quirk causes process inspection tools, like
+.Xr procstat 1 ,
+to report anonymous memory mappings instead of file mappings.
 .Sh OPTIONS
 The following options are available when
 mounting
 .Nm
 file systems:
-.Bl -tag -width indent
+.Bl -tag -width "It Cm maxfilesize"
 .It Cm gid
 Specifies the group ID of the root inode of the file system.
 Defaults to the mount point's GID.
@@ -92,6 +121,10 @@
 .It Cm mode
 Specifies the mode (in octal notation) of the root inode of the file system.
 Defaults to the mount point's mode.
+.It Cm nonc
+Do not use namecache to resolve names to files for the created mount.
+This saves memory, but currently might impair scalability for highly
+used mounts on large machines.
 .It Cm inodes
 Specifies the maximum number of nodes available to the file system.
 If not specified, the file system chooses a reasonable maximum based on
@@ -114,11 +147,15 @@
 .Pp
 .Dl "mount -t tmpfs tmpfs /tmp"
 .Sh SEE ALSO
+.Xr procstat 1 ,
+.Xr mmap 2 ,
 .Xr nmount 2 ,
 .Xr unmount 2 ,
 .Xr fstab 5 ,
 .Xr mdmfs 8 ,
-.Xr mount 8
+.Xr mount 8 ,
+.Xr swapinfo 8 ,
+.Xr swapon 8
 .Sh HISTORY
 The
 .Nm
@@ -130,7 +167,7 @@
 .Nm
 kernel implementation was written by
 .An Julio M. Merino Vidal Aq jmmv at NetBSD.org
-as a Google SoC project.
+as a Google Summer of Code project.
 .Pp
 .An Rohit Jalan
 and others ported it from
@@ -140,5 +177,3 @@
 .Pp
 This manual page was written by
 .An Xin LI Aq delphij at FreeBSD.org .
-.Sh BUGS
-Some file system mount time options may not be well-supported.


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