The tool I recommend is a [dwarven atom smasher][1].

First, you designate a 1x1 tile as a [dumping zone][2]

Second, and not necessarily in this order, you build a drawbridge that slams down on said tile.

Upon smashing down the drawbridge onto the tile, you obliterate anything smaller than an elephant (all items and any creature up to a zie of 1200000cm³). This can remove excess items, pets, population, invaders and consequently improve performance.

Note: If items end up being dumped onto an open drawbridge, raising the drawbridge will instead launch the items (and dwarves) in whatever direction the bridge closed.


  [1]: https://dwarffortresswiki.org/index.php/DF2014:Dwarven_atom_smasher
  [2]: https://dwarffortresswiki.org/index.php/Garbage_dump