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Diffstat (limited to 'Documentation/btrfs-man5.asciidoc')
| -rw-r--r-- | Documentation/btrfs-man5.asciidoc | 22 |
1 files changed, 17 insertions, 5 deletions
diff --git a/Documentation/btrfs-man5.asciidoc b/Documentation/btrfs-man5.asciidoc index a21d526d..e2eea263 100644 --- a/Documentation/btrfs-man5.asciidoc +++ b/Documentation/btrfs-man5.asciidoc @@ -278,13 +278,25 @@ May be resumed with *btrfs balance resume* or the paused state can be removed by *btrfs balance cancel*. *space_cache*:: +*space_cache=v2*:: *nospace_cache*:: -('nospace_cache' since: 3.2, default: on) +('nospace_cache' since: 3.2, 'space_cache=v2' since 4.5, default: on) + -Disable freespace cache loading without clearing the cache and the free space -cache will not be used during the mount. This affects performance as searching -for new free blocks could take longer. On the other hand, managing the space -cache consumes some resources. +Options to control the free space cache. This affects performance as searching +for new free blocks could take longer if the space cache is not enabled. On the +other hand, managing the space cache consumes some resources. It can be +disabled without clearing at mount time. ++ +There are two implementations of how the space is tracked. The safe default is +'v1'. On large filesystems (many-terabytes) and certain workloads the 'v1' +performance may degrade. This problem is addressed by 'v2', that is based on +b-trees, sometimes referred to as 'free-space-tree'. ++ +'Compatibility notes:' ++ +* the 'v2' has to be enabled manually at mount time, once +* kernel without 'v2' support will be able to mount the filesystem in read-only mode +* 'v2' can be removed by mounting with 'clear_cache' *ssd*:: *nossd*:: |