The category page aka product-list page was really slow to load, about 25 seconds plus
To troubleshoot Magento’s cpu usage, first enable varien profiler
You can also try aoe_profiler
Found out it was the configurable swatches.
Tried the first method in this post.
My load time went from 25s to 10s. Then I tried the 2nd post which points to https://github.com/wigman/AjaxSwatches
Load time went down 3s
BTW I am running Magento 18.104.22.168