On an 8gb machine, the browsing being bogged down probably doesn't have anything to do with memory usage. To figure out what is making everything slow, you need

On an 8gb machine, the browsing being bogged down probably doesn't have anything to do with memory usage. To figure out what is making everything slow, you need to use the built-in profiler with Nightly. I was able to use it to track down browser slowness I very occasionally see to a particular line of code on Facebook.