When usetex=True plotting is a lot slower than the normal.

I generated a simple testplot with some mathtex and timed the rendering time with usetex=True and usetex=False for both saving the plot and just displaying it:

import matplotlib.pyplot as plt
import matplotlib
import numpy as np
%matplotlib inline
x = np.linspace(0, 20, 500)
y = 3 * x + 0.5 * x**3 + 2

def plot(x, y):
    plt.plot(x, y)
    plt.title('simple testplot')
    plt.xlabel('$x$')
    plt.ylabel(r'$3 x + \frac{1}{2} x^3 + 2$')
    plt.savefig('test.pdf')

%timeit -n 1 -r 1 plot(x, y)

Here are the measurements:

• save pdf usetex=False: 351 ms
• save pdf usetex=True: 8.34 s
• display usetex=False: 39 ms
• display usetex=True: 38.3 ms but it took approx. 7 s until the plot was displayed

My system is running Mac OS X 10.10.4, matplotlib 1.4.3 and the latest LaTeX version.