Add note about hist speed for large number of bins

Author: Perseudonymous

lib/matplotlib/axes/_axes.py

@@ -6540,6 +6540,11 @@ def hist(self, x, bins=None, range=None, density=False, weights=None,
         --------
         hist2d : 2D histograms
 
+        Notes
+        -----
+        For large numbers of bins (>1000), 'step' and 'stepfilled' can be
+        significantly faster than 'bar' and 'barstacked'.
+
         """
         # Avoid shadowing the builtin.
         bin_range = range