High CPU usage by system
What you're seeing is not &quot;the system&quot; (as a separate entity) using up your CPU time so that &quot;your programs&quot; are not getting their fair share. This is not what happens.
In order to interpret the screenshot, you'll need to know that modern computers are designed to have their work load split between what is known as &quot;user space&quot; and &quot;system space&quot; (also known as kernel space). This is a form of protection.
The programs you're running will have their code running in &quot;user space&quot; consuming &quot;user CPU time&quot;. This would involve the various computations and data juggling that your program does by itself.
However most programs do not live on an island. They need to access privileged resources such as a reading files from a disk, sending information on a network, etc. To do this safely, they need to ask the system to perform these tasks for them. In doing so work is transitioned to &quot;system space&quot; and thus taking up &quot;system CPU time&quot;.
Activity Monitor shows you this split of your CPU usage. 70% is used in &quot;system space&quot;, 20% in &quot;user space&quot; and approx. 10% &quot;idle&quot; in your case.
This does not mean that &quot;the system&quot; is somehow sucking up 70% of the CPU time taking it away from your programs - rather it means your programs have asked the system to do stuff for them - and that takes 70% of the CPU time.
In the top part of Activity Monitor you'll see the percentages of CPU time that each program has used. This percentage is based on the SUM of the process' usage of both user and system CPU time.