Updated README with the performance notes

README.md

@@ -7,6 +7,24 @@ cd src
 python setup.py install --user
 ```
 
+Performance
+-----------
+
+For optimal performance results, we recommend the use of [PyPy](http://pypy.org).
+
+By default, PythonPDEVS is optimized for distributed simulation, therefore doing a lot of additional bookkeeping.
+For optimal performance in local simulations, we recommend the use of the *minimal* simulation kernel instead: just update all imports from
+```python
+from pypdevs.simulator import Simulator
+from pypdevs.DEVS import AtomicDEVS, CoupledDEVS
+```
+to
+```python
+from pypdevs.minimal import Simulator
+from pypdevs.minimal import AtomicDEVS, CoupledDEVS
+```
+Note that this disables many features.
+
 Distributed simulation (optional)
 ---------------------------------