Firefox eating memory and CPU fixed

Remove all old or unused plugins, then:

Firefox automatically uses settings that work best with your computer. You can modify these settings in your Firefox Preferences page. Click the menu button and choose Preferences. In the General panel, go down to the Performance section and uncheck the box next to Use recommended performance settings. You will then be able to change the following settings:

• Use hardware acceleration when available: This allows Firefox to use your computer's graphics processor, if possible, instead of the main processor, to display graphics-heavy web content such as videos or games. This frees up resources on your computer so it can run other applications, like Firefox, faster. This box is checked by default but the feature isn't available for all graphics processors. You must restart Firefox after changing this setting, before it will take effect.
• Content process limit: With Multiprocess Firefox, also called electrolysis or e10s , Firefox runs web content for all tabs separately from the main Firefox process for increased security and performance. Using multiple content processes can further increase performance and minimize the impact of content process crashes. You can modify this setting if multiprocess is enabled; however, having too many content processes can slow down your computer, and consequently, Firefox. The recommended maximum is four, but you can set up to seven. 

Add your :
about:config fix:
Solution:

Open Firefox and go to the Address Bar. Type in about:config and then press Enter.

Right Click in the page and select New -> Boolean.

In the box that pops up, enter config.trim_on_minimize. Press Enter.

Now select True and then press Enter.

Restart Firefox. 




about:memory: