title: When should I write a Linux kernel module?
body: <p>Some people want to move code from user space to kernel space in Linux for some reason. A lot of times the reason seems to be that the code should have particularly high priority or simply "kernel space is faster".</p>
  
  <p>This seems strange to me. When should I consider writing a kernel module? Are there a set of criterias?</p>
  
  <p>How can I motivate keeping code in user space that (I believe) belong there?</p>