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Re: Documenting MS_LAZYTIME

To: Theodore Ts'o <tytso@xxxxxxx>, Eric Sandeen <sandeen@xxxxxxxxxx>
Subject: Re: Documenting MS_LAZYTIME
From: Austin S Hemmelgarn <ahferroin7@xxxxxxxxx>
Date: Mon, 23 Feb 2015 07:20:41 -0500
Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx>, Ext4 Developers List <linux-ext4@xxxxxxxxxxxxxxx>, Linux btrfs Developers List <linux-btrfs@xxxxxxxxxxxxxxx>, XFS Developers <xfs@xxxxxxxxxxx>, linux-man@xxxxxxxxxxxxxxx, Linux-Fsdevel <linux-fsdevel@xxxxxxxxxxxxxxx>, Linux API <linux-api@xxxxxxxxxxxxxxx>
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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.

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