diff options
| author | David Sterba <dsterba@suse.com> | 2017-11-07 19:14:48 +0100 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2017-11-14 15:59:00 +0100 |
| commit | c9fa9355f39683fe6e294d16745427a6e42ba45a (patch) | |
| tree | 89032ed427dd532e0a6971d1661a7ac945ac7413 | |
| parent | 94856dd5476772a7fdba20adc1ad01543dc276c3 (diff) | |
btrfs-progs: docs: add impact of atime/noatime
Copy from wiki
https://btrfs.wiki.kernel.org/index.php?title=Mount_options
Signed-off-by: David Sterba <dsterba@suse.com>
| -rw-r--r-- | Documentation/btrfs-man5.asciidoc | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/Documentation/btrfs-man5.asciidoc b/Documentation/btrfs-man5.asciidoc index 5199f88b..bd005331 100644 --- a/Documentation/btrfs-man5.asciidoc +++ b/Documentation/btrfs-man5.asciidoc @@ -479,6 +479,25 @@ but will work on 4.5+ kernels. A workaround option from times (pre 3.2) when it was not possible to mount a subvolume that did not reside directly under the toplevel subvolume. +NOTES ON GENERIC MOUNT OPTIONS +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Some of the general mount options from `mount`(8) that affect BTRFS and are +worth mentioning. + +*noatime*:: +under read intensive work-loads, specifying 'noatime' significantly improves +performance because no new access time information needs to be written. Without +this option, the default is 'relatime', which only reduces the number of +inode atime updates in comparison to the traditional 'strictatime'. The worst +case for atime updates under 'relatime' occurs when many files are read whose +atime is older than 24 h and which are freshly snapshotted. In that case the +atime is updated 'and' COW happens - for each file - in bulk. See also +https://lwn.net/Articles/499293/ - 'Atime and btrfs: a bad combination? (LWN, 2012-05-31)'. ++ +Note that 'noatime' may break applications that rely on atime uptimes like +the venerable Mutt (unless you use maildir mailboxes). + FILESYSTEM FEATURES ------------------- |