As you saw, enabling compression means giving up CPU capacity to achieve reduced file sizes. Now that you have enabled compression, you will want to evaluate whether it works for you.
To see the difference in file size, use the Web Developer add-on for Firefox. We saw how to use this earlier on in the Pinpointing bottlenecks section.
To see the difference in CPU usage, stress test your site with compression switched off and then switched on (Chapter 14, Load Testing shows how to do a load test):