Operating System

• Many-to-one model

•Many user-level threads mapped to single kernel thre
ad–Thread management is done in user space
–Blocking problem
–No support for running in parallel on MP–Used on systems that do not support kernel threads.–Green-threads library in Solaris 2

• One-to One Model
  
  •Each user-level thread maps to a kernel thread–Creating a user thread r
  
  equires creating the corresponding kernel thread•Overhead–Restrict the number of threads supported by the OS•Examples
  
  –Windows NT/2000–OS/2

• Many-to Many
  •Multiplex many user-level threads to a smaller or equal number of kernel threads•Allows many user level threads to be mapped to many kernel threads.•Allows OS to create a sufficient number of kernel threads.•Examples–Solaris 2, IRIX, HP-UX, Tru64 UNIX–Windows NT/2000 with the ThreadFiber package