The MT Kernel

The MT kernel is a critical foundation of a complete multithreading implementation. In an MT kernel such as the one used by the Solaris operating environment, each kernel thread is a single flow of control within the kernel's address space. The kernel threads are fully preemptive and can be scheduled by any of the available scheduling classes in the system, including the real-time class. All execution entities are built using kernel threads, which represent a fully preemptive, real-time "nucleus" within the kernel.

In addition, kernel threads employ synchronization primitives that support protocols for preventing the blocking that results in the inversion of thread and process priority. This ensures that applications execute as expected. Kernel threads also allow kernel-level tasks such as NFS daemons, pageout daemons, and interrupts to execute asynchronously, thus increasing concurrency and overall throughput.

The MT kernel is essential to building an MT application architecture, such as a typical JVM implementation:

• It is fully symmetric in order to maximize multiprocessor performance.

• With its multiple kernel threads, it enables parallelism on multiprocessor machines. This improves the efficiency of hardware subsystems by providing concurrency and parallelism in computation, networking, display, and I/O.

• Traditional (single-threaded) applications run unchanged on an MT kernel.

• It is fully preemptive, providing real-time responsiveness.