Documenting MS_LAZYTIME

[Austin S Hemmelgarn]

On 2015-02-20 21:56, Theodore Ts'o wrote:
> On Fri, Feb 20, 2015 at 09:49:34AM -0600, Eric Sandeen wrote:
>>
>>>                This mount option significantly reduces  writes  to  the
>>>                inode  table  for workloads that perform frequent random
>>>                writes to preallocated files.
>>
>> This seems like an overly specific description of a single workload out
>> of many which may benefit, but what do others think?  "inode table" is also
>> fairly extN-specific.
>
> How about somethign like "This mount significantly reduces writes
> needed to update the inode's timestamps, especially mtime and actime.
> Examples of workloads where this could be a large win include frequent
> random writes to preallocated files, as well as cases where the
> MS_STRICTATIME mount option is enabled."?
>
> (The advantage of MS_STRICTATIME | MS_LAZYTIME is that stat system
> calls will return the correctly updated atime, but those atime updates
> won't get flushed to disk unless the inode needs to be updated for
> file system / data consistency reasons, or when the inode is pushed
> out of memory, or when the file system is unmounted.)
>
If you want to list some specific software, it should help with anything 
that uses sqlite (which notably includes firefox and chrome), as well as 
most RDMS software and systemd-journald.