I was working on a vacation plan with 20 to 30 tabs open in safari quite often recently, during which I discovered safari really struggled with such amount of contents. My macbook pro is 2010 with 8G ram and 512G SSD. The ram usage of Safari was about 1.5 to 1.8G, which should be fine considering I only had iTunes and a few other insignificant apps running. So I am wondering if there is a restriction to the available resource located to Safari. I transferred half of tabs (about 10+) to Chrome and had both browsers running parallel. My system and both browsers worked just fine.