• Qu Wenruo's avatar
    btrfs: qgroup: Move half of the qgroup accounting time out of commit trans · fb235dc0
    Qu Wenruo authored
    Just as Filipe pointed out, the most time consuming parts of qgroup are
    btrfs_qgroup_account_extents() and
    btrfs_qgroup_prepare_account_extents().
    Which both call btrfs_find_all_roots() to get old_roots and new_roots
    ulist.
    
    What makes things worse is, we're calling that expensive
    btrfs_find_all_roots() at transaction committing time with
    TRANS_STATE_COMMIT_DOING, which will blocks all incoming transaction.
    
    Such behavior is necessary for @new_roots search as current
    btrfs_find_all_roots() can't do it correctly so we do call it just
    before switch commit roots.
    
    However for @old_roots search, it's not necessary as such search is
    based on commit_root, so it will always be correct and we can move it
    out of transaction committing.
    
    This patch moves the @old_roots search part out of
    commit_transaction(), so in theory we can half the time qgroup time
    consumption at commit_transaction().
    
    But please note that, this won't speedup qgroup overall, the total time
    consumption is still the same, just reduce the performance stall.
    
    Cc: Filipe Manana <fdmanana@suse.com>
    Signed-off-by: default avatarQu Wenruo <quwenruo@cn.fujitsu.com>
    Reviewed-by: default avatarFilipe Manana <fdmanana@suse.com>
    Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
    fb235dc0
qgroup.c 74.7 KB