Documentation/filesystems/tmpfs.rst

1 .. SPDX-License-Identifier: GPL-2.0
14 tmpfs puts everything into the kernel internal caches and grows and
21 fly using a remount ('mount -o remount ...') of the filesystem. A tmpfs
45 1) There is always a kernel internal mount which you will not see at
63    mount is used for that. (In the 2.3 kernel versions it was
72 4) And probably a lot more I do not know about :-)
101 extended attributes: "df -i"'s IUsed and IUse% increase, IFree decreases.
111 tmpfs also supports Transparent Huge Pages which requires a kernel
124 See also Documentation/admin-guide/mm/transhuge.rst, which describes the
125 sysfs file /sys/kernel/mm/transparent_hugepage/shmem_enabled: which can
150 quota entry for user/group/project id is being accessed - typically the
160 tmpfs has a mount option to set the NUMA memory allocation policy for
161 all files in that instance (if CONFIG_NUMA is enabled) - which can be
162 adjusted on the fly via 'mount -o remount ...'
165 mpol=default             use the process allocation policy
174 NodeList format is a comma-separated list of decimal numbers and ranges,
175 a range being two hyphen-separated decimal numbers, the smallest and
176 largest node numbers in the range.  For example, mpol=bind:0-3,5,7,9-15
178 A memory policy with a valid NodeList will be saved, as specified, for
180 system, the mount option memory policy will be applied with a NodeList,
182 [See Documentation/admin-guide/cgroup-v1/cpusets.rst] and any optional flags,
184 memory policy for the file will revert to "default" policy.
189 See Documentation/admin-guide/mm/numa_memory_policy.rst for a list of
190 all available memory allocation policy mode flags and their effect on
191 memory policy.
199 allocation policy of MPOL_BIND | MPOL_F_STATIC_NODES.
202 running kernel does not support NUMA; and will fail if its nodelist
204 tmpfs being mounted, but from time to time runs a kernel built without
205 NUMA capability (perhaps a safe recovery kernel), or with fewer nodes
208 on MountPoint, by 'mount -o remount,mpol=Policy:NodeList MountPoint'.
224 tmpfs has a mount option to select whether it will wrap at 32- or 64-bit inode
228 inode64   Use 64-bit inode numbers
229 inode32   Use 32-bit inode numbers
232 On a 32-bit kernel, inode32 is implicit, and inode64 is refused at mount time.
233 On a 64-bit kernel, CONFIG_TMPFS_INODE64 sets the default.  inode64 avoids the
235 but risks glibc failing with EOVERFLOW once 33-bit inode numbers are reached -
236 if a long-lived tmpfs is accessed by 32-bit applications so ancient that
240 So 'mount -t tmpfs -o size=10G,nr_inodes=10k,mode=700 tmpfs /mytmpfs'