Green threads is
thread mechanism implemented in JVM itself. It is blind and can run on any OS, so actually all threads are run in one native thread and scheduling is up to JVM.
This is disadvantageously for SMP systems, since only one processor can serve
Java application.
Native threads is a mechanism based on OS threading mechanism. This allows to use features of hardware and OS. For example,there is IBM's JDK for AIX that supports native threads. The perfomance of applications can be highly imploved by this.
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With best of best regards, Pawel S. Veselov ( aka Black Angel )