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hugetlbfs: document min_size mount option and cleanup

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Add min_size mount option to the hugetlbfs documentation.  Also, add the
missing pagesize option and mention that size can be specified as bytes or
a percentage of huge page pool.

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mike Kravetz 2015-04-15 16:13:45 -07:00 committed by Linus Torvalds
parent 7ca02d0ae5
commit 8c9b970335
1 changed files with 22 additions and 9 deletions
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31
Documentation/vm/hugetlbpage.txt
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@ -267,21 +267,34 @@ call, then it is required that system administrator mount a file system of
type hugetlbfs:
mount -t hugetlbfs \
-o uid=<value>,gid=<value>,mode=<value>,size=<value>,nr_inodes=<value> \
none /mnt/huge
-o uid=<value>,gid=<value>,mode=<value>,pagesize=<value>,size=<value>,\
min_size=<value>,nr_inodes=<value> none /mnt/huge
This command mounts a (pseudo) filesystem of type hugetlbfs on the directory
/mnt/huge. Any files created on /mnt/huge uses huge pages. The uid and gid
options sets the owner and group of the root of the file system. By default
the uid and gid of the current process are taken. The mode option sets the
mode of root of file system to value & 01777. This value is given in octal.
By default the value 0755 is picked. The size option sets the maximum value of
memory (huge pages) allowed for that filesystem (/mnt/huge). The size is
rounded down to HPAGE_SIZE. The option nr_inodes sets the maximum number of
inodes that /mnt/huge can use. If the size or nr_inodes option is not
provided on command line then no limits are set. For size and nr_inodes
options, you can use [G|g]/[M|m]/[K|k] to represent giga/mega/kilo. For
example, size=2K has the same meaning as size=2048.
By default the value 0755 is picked. If the paltform supports multiple huge
page sizes, the pagesize option can be used to specify the huge page size and
associated pool. pagesize is specified in bytes. If pagesize is not specified
the paltform's default huge page size and associated pool will be used. The
size option sets the maximum value of memory (huge pages) allowed for that
filesystem (/mnt/huge). The size option can be specified in bytes, or as a
percentage of the specified huge page pool (nr_hugepages). The size is
rounded down to HPAGE_SIZE boundary. The min_size option sets the minimum
value of memory (huge pages) allowed for the filesystem. min_size can be
specified in the same way as size, either bytes or a percentage of the
huge page pool. At mount time, the number of huge pages specified by
min_size are reserved for use by the filesystem. If there are not enough
free huge pages available, the mount will fail. As huge pages are allocated
to the filesystem and freed, the reserve count is adjusted so that the sum
of allocated and reserved huge pages is always at least min_size. The option
nr_inodes sets the maximum number of inodes that /mnt/huge can use. If the
size, min_size or nr_inodes option is not provided on command line then
no limits are set. For pagesize, size, min_size and nr_inodes options, you
can use [G|g]/[M|m]/[K|k] to represent giga/mega/kilo. For example, size=2K
has the same meaning as size=2048.
While read system calls are supported on files that reside on hugetlb
file systems, write system calls are not.