title: What does the "System" category of records mean in Chrome Timeline profiling tool?
body: <p>I'm trying to understand how the speed of a D3.js application (an interactive visualisation of data) could be improved by analysing the Timeline data in Chrome Developer Tool.</p>
  
  <p>I'm dragging the data bars around, them being moved (SVG transformations) on mousemove events.</p>
  
  <p>Timeline tells me that 50% of CPU time is being used by "System" processes (the rest being "Scripting", "Rendering", "Painting", and "Idle").</p>
  
  <p>What exactly is "System", and what could be the problem, if it takes 50% of time?</p>
  
  <p>By the way, if I'm dragging by holding the right mouse button not left, the response is much better, and "System" uses only about 20% of time.</p>
  
  <blockquote>
    <p>2020 note: in old Chrome the "System" category was named "Other".</p>
  </blockquote>