From 2f732723d6c1e3b6e9205e96da4c600ee72de875 Mon Sep 17 00:00:00 2001 From: David Sterba Date: Thu, 28 Jul 2016 13:14:08 +0200 Subject: btrfs-progs: fi defrag: change default extent target size to 32 MiB The kernel default is too low, 32 MiB is recommended and should give better results. Signed-off-by: David Sterba --- Documentation/btrfs-filesystem.asciidoc | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) (limited to 'Documentation') diff --git a/Documentation/btrfs-filesystem.asciidoc b/Documentation/btrfs-filesystem.asciidoc index 8fb15eac..9782af9b 100644 --- a/Documentation/btrfs-filesystem.asciidoc +++ b/Documentation/btrfs-filesystem.asciidoc @@ -117,15 +117,23 @@ compression. See also section 'EXAMPLES'. -r:::: defragment files recursively in given directories -f:::: -flush data for each file before going to the next file. This will limit the amount -of dirty data to current file, otherwise the amount cumulates from several files -and may increase system load. +flush data for each file before going to the next file. ++ +This will limit the amount of dirty data to current file, otherwise the amount +cumulates from several files and will increase system load. This can also lead +to ENOSPC if there's too much dirty data to write and it's not possible to make +the reservations for the new data (ie. how the COW design works). ++ -s [kKmMgGtTpPeE]:::: defragmentation will start from the given offset, default is beginning of a file -l [kKmMgGtTpPeE]:::: defragment only up to 'len' bytes, default is the file size -t [kKmMgGtTpPeE]:::: -target extent size, do not touch extents bigger than 'size' +target extent size, do not touch extents bigger than 'size', default: 32M ++ +The value is only advisory and the final size of the extents may differ, +depending on the state of the free space and fragmentation or other internal +logic. Reasonable values are from tens to hundreds of megabytes. *du* [options] [..]:: Calculate disk usage of the target files using FIEMAP. For individual -- cgit v1.2.3