tmpfs /dev/shm tmpfs defaults 0 0
Remember to create the directory that you intend to mount tmpfs on
- if necessary (/dev/shm is automagically created if you use devfs).
+ if necessary.
This mount is _not_ needed for SYSV shared memory. The internal
mount is used for that. (In the 2.3 kernel versions it was
nr_blocks: The same as size, but in blocks of PAGE_CACHE_SIZE.
nr_inodes: The maximum number of inodes for this instance. The default
is half of the number of your physical RAM pages, or (on a
- a machine with highmem) the number of lowmem RAM pages,
+ machine with highmem) the number of lowmem RAM pages,
whichever is the lower.
These parameters accept a suffix k, m or g for kilo, mega and giga and
to limit this tmpfs instance to that percentage of your physical RAM:
the default, when neither size nor nr_blocks is specified, is size=50%
-If both nr_blocks (or size) and nr_inodes are set to 0, neither blocks
-nor inodes will be limited in that instance. It is generally unwise to
+If nr_blocks=0 (or size=0), blocks will not be limited in that instance;
+if nr_inodes=0, inodes will not be limited. It is generally unwise to
mount with such options, since it allows any user with write access to
use up all the memory on the machine; but enhances the scalability of
that instance in a system with many cpus making intensive use of it.
+tmpfs has a mount option to set the NUMA memory allocation policy for
+all files in that instance (if CONFIG_NUMA is enabled) - which can be
+adjusted on the fly via 'mount -o remount ...'
+
+mpol=default prefers to allocate memory from the local node
+mpol=prefer:Node prefers to allocate memory from the given Node
+mpol=bind:NodeList allocates memory only from nodes in NodeList
+mpol=interleave prefers to allocate from each node in turn
+mpol=interleave:NodeList allocates from each node of NodeList in turn
+
+NodeList format is a comma-separated list of decimal numbers and ranges,
+a range being two hyphen-separated decimal numbers, the smallest and
+largest node numbers in the range. For example, mpol=bind:0-3,5,7,9-15
+
+NUMA memory allocation policies have optional flags that can be used in
+conjunction with their modes. These optional flags can be specified
+when tmpfs is mounted by appending them to the mode before the NodeList.
+See Documentation/vm/numa_memory_policy.txt for a list of all available
+memory allocation policy mode flags.
+
+ =static is equivalent to MPOL_F_STATIC_NODES
+ =relative is equivalent to MPOL_F_RELATIVE_NODES
+
+For example, mpol=bind=static:NodeList, is the equivalent of an
+allocation policy of MPOL_BIND | MPOL_F_STATIC_NODES.
+
+Note that trying to mount a tmpfs with an mpol option will fail if the
+running kernel does not support NUMA; and will fail if its nodelist
+specifies a node which is not online. If your system relies on that
+tmpfs being mounted, but from time to time runs a kernel built without
+NUMA capability (perhaps a safe recovery kernel), or with fewer nodes
+online, then it is advisable to omit the mpol option from automatic
+mount options. It can be added later, when the tmpfs is already mounted
+on MountPoint, by 'mount -o remount,mpol=Policy:NodeList MountPoint'.
+
+
To specify the initial root directory you can use the following mount
options:
Author:
Christoph Rohland <cr@sap.com>, 1.12.01
Updated:
- Hugh Dickins <hugh@veritas.com>, 01 September 2004
+ Hugh Dickins, 4 June 2007