This has been an ongoing issue with X11 compositers like marco, unity and cinnamon etc... Ifind especially with an Nvidia GPU that as the system runs longer after a number of weeks or a number of months the GUI just gets slower and slower. It's not something you'll instantly notice but just a hint of lag here or there that gets worse.
One hint you'll find is by watching nvidia-smi and checking the utilization you will start seeing random spikes of 80-100% even without maxi........
This server was experiencing loads of up to 80 and maxing out the RAM and kmemsize on a CPanel VPS. There were literally dozens if not hundreds of exim processes. I have no idea why exim has such a design that would allow it to consume this much CPU and RAM. Any normal MTA should not be spawning so many processes, it should be processing them in sequence and if it is going to spawn hundreds of processes in response to a large volume of mail, it's better to have a delayed del........