I recently upgraded to High Sierra and after upgrading I've run into an issue where after the machine has been up for several days, the performance starts to get really bad. For example, when typing, characters appear really slowly and it takes about 5 or 10 seconds for them to all appear. Other aspects of machine are poor, such as web pages taking a while to load and render. Menu picks can take 10 seconds for menu to popup. However, the mouse tracks movement normally and is responsive. In general, the whole machine's performance is extremely poor. Looking at the
Activity Monitor the cpu load is normal and the memory pressure is normal, so I'm stumped as to what is going wrong.
The only way I've found to resolve the issue is to reboot. If I logout and login again, the problem persists.
The issue seems related to the web browsers Chrome or Safari as quitting these seems to alleviate the problem and get performance back to normal, however, relaunching results in the issue returning until reboot is performed.
The issue seems related to the external display, as moving from one external display with laptop closed to another with the laptop still closed seems to trigger the issue. I've found in at least one case that opening the laptop and getting it to render and then closing laptop again seems to cause the issue to go away.
What is going on that would give extremely slow performance yet not be evidenced in CPU load or memory pressure?