• Josef Bacik's avatar
    Btrfs: add a incompatible format change for smaller metadata extent refs · 3173a18f
    Josef Bacik authored
    We currently store the first key of the tree block inside the reference for the
    tree block in the extent tree.  This takes up quite a bit of space.  Make a new
    key type for metadata which holds the level as the offset and completely removes
    storing the btrfs_tree_block_info inside the extent ref.  This reduces the size
    from 51 bytes to 33 bytes per extent reference for each tree block.  In practice
    this results in a 30-35% decrease in the size of our extent tree, which means we
    COW less and can keep more of the extent tree in memory which makes our heavy
    metadata operations go much faster.  This is not an automatic format change, you
    must enable it at mkfs time or with btrfstune.  This patch deals with having
    metadata stored as either the old format or the new format so it is easy to
    convert.  Thanks,
    Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
    3173a18f
disk-io.c 107 KB