I did a bit more digging.  Using Ubuntu 15.10 64 bit on a system with Intel HD4000 graphics.  I was getting about one frame every 3 seconds and the system felt very unresponsive (eg takes a minute or two to kill the tab).  But the mouse pointer moved.<p>Connecting in via ssh showed that the system was just fine and close to idle.  It was the GPU where the issues are.  I ran intel_gpu_top and what you see is that render busy is at 100% as is blitter busy (most of the time).  Essentially the gpu is saturated.  I do wonder if this is similar to bufferbloat, but with so much work pending for the gpu that other requests take a long time to run.<p>I ended up having to kill -9 chrome, and ended up with a hung system (ie even magic sysrq didn&#x27;t work).