[CentOS] Desktop lag with CentOS7/Mate and high CPU usage

We have noticed significant desktop/UI lag on CentOS7 workstations using 
Mate when the CPU usage is high - i.e. the mouse pointer lags and moving 
windows (e.g. terminal windows) become jumpy (not smooth)

We didn't see (or notice) this issue with CentOS6/Gnome2

This can easily be shown by running something like 'cpuburn' 
(https://patrickmn.com/projects/cpuburn/) and moving a mate-terminal 
window around the screen

We can make things 'better' by running CPU intensive apps via 'nice' 
(without any noticeable performance hit to the CPU intensive app) - but 
this is a rather messy way of fixing the issue

We can also make things better by renice'ing X to a negative nice level

However, both these approaches seem wrong to me - as I'm probably 
missing something straightforward here

Does anyone know of any CentOS7/Mate settings that could be used to 
improve desktop/UI responsiveness with high CPU usage ?

Thanks

James Pearson