linux-kernel - Re: [PATCH V2 4/4] hugetlbfs: document min

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Message-ID: <550A2B9A.3060905@oracle.com>
Date:	Wed, 18 Mar 2015 18:51:22 -0700
From:	Mike Kravetz <mike.kravetz@...cle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Davidlohr Bueso <dave@...olabs.net>,
	Aneesh Kumar <aneesh.kumar@...ux.vnet.ibm.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH V2 4/4] hugetlbfs: document min_size mount option

On 03/18/2015 02:41 PM, Andrew Morton wrote:
> On Mon, 16 Mar 2015 16:53:29 -0700 Mike Kravetz <mike.kravetz@...cle.com> wrote:
>
>> Update documentation for the hugetlbfs min_size mount option.
>>
>> Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
>> ---
>>   Documentation/vm/hugetlbpage.txt | 21 ++++++++++++++-------
>>   1 file changed, 14 insertions(+), 7 deletions(-)
>>
>> diff --git a/Documentation/vm/hugetlbpage.txt b/Documentation/vm/hugetlbpage.txt
>> index f2d3a10..83c0305 100644
>> --- a/Documentation/vm/hugetlbpage.txt
>> +++ b/Documentation/vm/hugetlbpage.txt
>> @@ -267,8 +267,8 @@ 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>,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
>> @@ -277,11 +277,18 @@ 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.
>> +rounded down to HPAGE_SIZE.  The min_size option sets the minimum value of
>> +memory (huge pages) allowed for the filesystem.  Like the size option,
>> +min_size is rounded down to HPAGE_SIZE.  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 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.
>
> Nowhere here is the reader told the units of "size".  We should at
> least describe that, and maybe even rename the thing to min_bytes.
>

Ok, I will add that the size is in unit of bytes.  My choice of
'min_size' as a name for the new mount option was influenced by
the existing 'size' mount option.  I'm open to any suggestions
for the name of this new mount option.

-- 
Mike Kravetz
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