I have noticed on my MacBook 5,1 with 4 GB of RAM that Safari gets sluggish in full screen mode with twelve tabs open. I also noticed that Safari 5.1, which ships with Mac OS X Lion, spins two processes: Safari (currently using 294 MB RAM and 6.2% of CPU utilization) and Safari Web Content (currently using 1.33 GB RAM and 41% of CPU utilization). If I drop out of full screen mode, the RAM allocation remains the same, but the CPU utilization drops to about 1.4% and 8% respectively. Now, I am back into full screen mode, but I have not yet seen the spike in CPU utilization. I currently have three Safari Extensions installed: AdBlock, Awesome Screenshot, and Click to Flash. I also have the latest version of Adobe Flash installed, but I do not have any active Flash content loaded.
I searched online to see if anyone else is having similar issues. I found a thread started by scryedz on the Apple Support Communities, who began the discussion by writing:
Hi everyone! Safari become very lag when I open a new tab or pages, and when I checked Activity Monitor, the one that made my mac lag is Safari Web Content, it can eats 80-90% of CPU.However, it only happened if I open new tab/pages. I never experienced lag with other browser such as Firefox before. Anyone ever experienced this? Any suggestion or solution will be appreciated. Thanks.
via Safari Web Content high CPU usage: Apple Support Communities.
Following the thread, it sounds like others are experiencing Safari’s resource hogging and system sluggishness. Some suggestions to fix the problem include deleting Safari’s cache files manually (~User/Library/Cache/com.Apple.Safari) and uninstalling all Safari Extensions.
Hopefully, Apple will address this problem more assertively with a software update to Safari.