2 .\" Copyright (c) 2007 Xin LI
3 .\" Copyright (c) 2017 The FreeBSD Foundation, Inc.
5 .\" Part of this documentation was written by
6 .\" Konstantin Belousov <kib@FreeBSD.org> under sponsorship
7 .\" from the FreeBSD Foundation.
9 .\" Redistribution and use in source and binary forms, with or without
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61 .Nd "in-memory file system"
63 To compile this driver into the kernel,
64 place the following line in your
65 kernel configuration file:
66 .Bd -ragged -offset indent
70 Alternatively, to load the driver as a
71 module at boot time, place the following line in
73 .Bd -literal -offset indent
79 driver implements an in-memory, or
82 The filesystem stores both file metadata and data in main memory.
83 This allows very fast and low latency accesses to the data.
85 An umount or system reboot invalidates it.
86 These properties make the filesystem's mounts suitable for fast
90 If the system becomes low on memory and swap is configured
93 the system can transfer file data to swap space, freeing memory
95 Metadata, including the directory content, is never swapped out by the
96 current implementation.
97 Keep this in mind when planning the mount limits, especially when expecting
98 to place many small files on a tmpfs mount.
102 is used on a file from a tmpfs mount, the swap VM object managing the
103 file pages is used to implement mapping and avoid double-copying of
105 This quirk causes process inspection tools, like
107 to report anonymous memory mappings instead of file mappings.
109 The following options are available when
113 .Bl -tag -width "It Cm maxfilesize"
115 Specifies the group ID of the root inode of the file system.
116 Defaults to the mount point's GID.
118 Specifies the user ID of the root inode of the file system.
119 Defaults to the mount point's UID.
121 Specifies the mode (in octal notation) of the root inode of the file system.
122 Defaults to the mount point's mode.
124 Do not use namecache to resolve names to files for the created mount.
125 This saves memory, but currently might impair scalability for highly
126 used mounts on large machines.
128 Specifies the maximum number of nodes available to the file system.
129 If not specified, the file system chooses a reasonable maximum based on
130 the file system size, which can be limited with the
134 Specifies the total file system size in bytes, unless suffixed
135 with one of k, m, g, t, or p, which denote byte, kilobyte,
136 megabyte, gigabyte, terabyte and petabyte respectively.
137 If zero (the default) or a value larger than SIZE_MAX - PAGE_SIZE
138 is given, the available amount of memory (including
139 main memory and swap space) will be used.
141 Specifies the maximum file size in bytes.
142 Defaults to the maximum possible value.
144 Specifies the maximum memory size used by extended attributes in bytes.
145 Defaults to 16 megabytes.
152 .Dl "mount -t tmpfs tmpfs /tmp"
158 .Bd -literal -offset indent
159 tmpfs /tmp tmpfs rw 0 0
174 driver first appeared in
180 kernel implementation was written by
181 .An Julio M. Merino Vidal Aq Mt jmmv@NetBSD.org
182 as a Google Summer of Code project.
185 and others ported it from
190 This manual page was written by
191 .An Xin LI Aq Mt delphij@FreeBSD.org .