Plotting large-ish arrays using pcolormesh with current (e2c5918) matplotlib master looks like it might have a memory leak. Running the following code on matplotlib v1.3.1 produces a QuadMesh in approximately a second. However running the same code on matplotlib master floods the memory until either the pcolormesh call is aborted or it runs out of memory.

import matplotlib.pyplot as plt
import numpy as np

data = np.random.rand(3000*3000).reshape(3000, 3000)
plt.pcolormesh(data)
plt.show()