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author | Hugh Dickins <hughd@google.com> | 2023-07-23 13:55:00 -0700 |
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committer | Andrew Morton <akpm@linux-foundation.org> | 2023-07-27 13:07:03 -0700 |
commit | 253e5df8b8f0145adb090f57c6f4e6efa52d738e (patch) | |
tree | a1e684c4081ebe2b82bfa1cb7b64be1458ef3850 /Documentation/filesystems/tmpfs.rst | |
parent | dddfa05eb58076ad60f9a66e7155a5b3502b2dd5 (diff) | |
download | linux-stable-253e5df8b8f0145adb090f57c6f4e6efa52d738e.tar.gz linux-stable-253e5df8b8f0145adb090f57c6f4e6efa52d738e.tar.bz2 linux-stable-253e5df8b8f0145adb090f57c6f4e6efa52d738e.zip |
tmpfs: fix Documentation of noswap and huge mount options
The noswap mount option is surely not one of the three options for sizing:
move its description down.
The huge= mount option does not accept numeric values: those are just in
an internal enum. Delete those numbers, and follow the manpage text more
closely (but there's not yet any fadvise() or fcntl() which applies here).
/sys/kernel/mm/transparent_hugepage/shmem_enabled is hard to describe, and
barely relevant to mounting a tmpfs: just refer to transhuge.rst (while
still using the words deny and force, to help as informal reminders).
[rdunlap@infradead.org: fixup Docs table for huge mount options]
Link: https://lkml.kernel.org/r/20230725052333.26857-1-rdunlap@infradead.org
Link: https://lkml.kernel.org/r/986cb0bf-9780-354-9bb-4bf57aadbab@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Fixes: d0f5a85442d1 ("shmem: update documentation")
Fixes: 2c6efe9cf2d7 ("shmem: add support to ignore swap")
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'Documentation/filesystems/tmpfs.rst')
-rw-r--r-- | Documentation/filesystems/tmpfs.rst | 47 |
1 files changed, 20 insertions, 27 deletions
diff --git a/Documentation/filesystems/tmpfs.rst b/Documentation/filesystems/tmpfs.rst index f18f46be5c0c..2cd8fa332feb 100644 --- a/Documentation/filesystems/tmpfs.rst +++ b/Documentation/filesystems/tmpfs.rst @@ -84,8 +84,6 @@ 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 machine with highmem) the number of lowmem RAM pages, whichever is the lower. -noswap Disables swap. Remounts must respect the original settings. - By default swap is enabled. ========= ============================================================ These parameters accept a suffix k, m or g for kilo, mega and giga and @@ -99,36 +97,31 @@ 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 blocks may be swapped out, when there is a shortage of memory. +tmpfs has a mount option to disable its use of swap: + +====== =========================================================== +noswap Disables swap. Remounts must respect the original settings. + By default swap is enabled. +====== =========================================================== + tmpfs also supports Transparent Huge Pages which requires a kernel configured with CONFIG_TRANSPARENT_HUGEPAGE and with huge supported for your system (has_transparent_hugepage(), which is architecture specific). The mount options for this are: -====== ============================================================ -huge=0 never: disables huge pages for the mount -huge=1 always: enables huge pages for the mount -huge=2 within_size: only allocate huge pages if the page will be - fully within i_size, also respect fadvise()/madvise() hints. -huge=3 advise: only allocate huge pages if requested with - fadvise()/madvise() -====== ============================================================ - -There is a sysfs file which you can also use to control system wide THP -configuration for all tmpfs mounts, the file is: - -/sys/kernel/mm/transparent_hugepage/shmem_enabled - -This sysfs file is placed on top of THP sysfs directory and so is registered -by THP code. It is however only used to control all tmpfs mounts with one -single knob. Since it controls all tmpfs mounts it should only be used either -for emergency or testing purposes. The values you can set for shmem_enabled are: - -== ============================================================ --1 deny: disables huge on shm_mnt and all mounts, for - emergency use --2 force: enables huge on shm_mnt and all mounts, w/o needing - option, for testing -== ============================================================ +================ ============================================================== +huge=never Do not allocate huge pages. This is the default. +huge=always Attempt to allocate huge page every time a new page is needed. +huge=within_size Only allocate huge page if it will be fully within i_size. + Also respect madvise(2) hints. +huge=advise Only allocate huge page if requested with madvise(2). +================ ============================================================== + +See also Documentation/admin-guide/mm/transhuge.rst, which describes the +sysfs file /sys/kernel/mm/transparent_hugepage/shmem_enabled: which can +be used to deny huge pages on all tmpfs mounts in an emergency, or to +force huge pages on all tmpfs mounts for testing. 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 |