Thread (4 messages) 4 messages, 3 authors, 2015-02-27

Re: Documenting MS_LAZYTIME

From: Michael Kerrisk (man-pages) <hidden>
Date: 2015-02-26 08:49:39
Also in: linux-btrfs, linux-ext4, linux-fsdevel, linux-man, linux-xfs

Possibly related (same subject, not in this thread)

Ted,

On 02/21/2015 03:56 AM, Theodore Ts'o wrote:
On Fri, Feb 20, 2015 at 09:49:34AM -0600, Eric Sandeen wrote:
quoted
quoted
              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.
What is "actime" in the preceding line? Should it be "ctime"?
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."?
I think some version of the following text could also usefully go 
into the page, but...
(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.)
I find the wording of there a little confusing. Is the following 
a correct rewrite:

    The advantage of MS_STRICTATIME | MS_LAZYTIME is that stat(2)
    will return the correctly updated atime, but the atime updates
    will be flushed to disk only when (1) the inode needs to be 
    updated for filesystem / data consistency reasons or (2) the 
    inode is pushed out of memory, or (3) the filesystem is 
    unmounted.)

?

Thanks,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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