fedora core 6 1.2949 + vserver 2.2.0

[linux-2.6.git] / Documentation / filesystems / tmpfs.txt

diff --git a/Documentation/filesystems/tmpfs.txt b/Documentation/filesystems/tmpfs.txt
index 177edbe..6dd0508 100644 (file)
--- a/Documentation/filesystems/tmpfs.txt
+++ b/Documentation/filesystems/tmpfs.txt
@@ -39,7 +39,7 @@ tmpfs has the following uses:
        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
@@ -62,13 +62,45 @@ size:      The limit of allocated bytes for this tmpfs instance. The
            since the OOM handler will not be able to free that memory.
 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.
+           is half of the number of your physical RAM pages, or (on a
+           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
 can be changed on remount.  The size parameter also accepts a suffix %
 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 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
+
+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 >= MAX_NUMNODES.  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 configured to support
+fewer nodes, 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:
@@ -89,4 +121,4 @@ RAM/SWAP in 10240 inodes and it is only accessible by root.
 Author:
    Christoph Rohland <cr@sap.com>, 1.12.01
 Updated:
-   Hugh Dickins <hugh@veritas.com>, 01 April 2003
+   Hugh Dickins <hugh@veritas.com>, 19 February 2006