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Diffstat (limited to 'Documentation/filesystems/tmpfs.txt')
| -rw-r--r-- | Documentation/filesystems/tmpfs.txt | 60 |
1 files changed, 48 insertions, 12 deletions
diff --git a/Documentation/filesystems/tmpfs.txt b/Documentation/filesystems/tmpfs.txt index dbe4d87d261..98ef5512415 100644 --- 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 @@ -63,7 +63,7 @@ size: The limit of allocated bytes for this tmpfs instance. The 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 @@ -79,15 +79,49 @@ 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: -mpol=interleave prefers to allocate memory from each node in turn -mpol=default prefers to allocate memory from the local node -mpol=bind prefers to allocate from mpol_nodelist -mpol=preferred prefers to allocate from first node in mpol_nodelist - -The following mount option is used in conjunction with mpol=interleave, -mpol=bind or mpol=preferred: -mpol_nodelist: nodelist suitable for parsing with nodelist_parse. +all files in that instance (if CONFIG_NUMA is enabled) - which can be +adjusted on the fly via 'mount -o remount ...' + +mpol=default use the process allocation policy + (see set_mempolicy(2)) +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 +mpol=local prefers to allocate memory from the local node + +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 + +A memory policy with a valid NodeList will be saved, as specified, for +use at file creation time. When a task allocates a file in the file +system, the mount option memory policy will be applied with a NodeList, +if any, modified by the calling task's cpuset constraints +[See Documentation/cgroups/cpusets.txt] and any optional flags, listed +below. If the resulting NodeLists is the empty set, the effective memory +policy for the file will revert to "default" policy. + +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 and their effect on memory policy. + + =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 @@ -109,4 +143,6 @@ 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>, 13 March 2005 + Hugh Dickins, 4 June 2007 +Updated: + KOSAKI Motohiro, 16 Mar 2010 |