Many-to-One Model (Green Threads)

Implementations of the many-to-one model a lot of user threads to one kernel thread permit the application to create any number of threads that can perform concurrently. In a many-to-one (user-level threads) execution, every threads activity is restricted to user space. In addition, merely one thread at a time can access the kernel, thus only one schedulable entity is known to the operating system. Consequently, this multithreading model supply limited concurrency and doesn't exploit multiprocessors. The preliminary implementation of Java threads on the Solaris system was many-to-one as shown in the following figure.

Many-to-One Multithreading Model