System Contention Scope

The System Contention Scope is a scheme that determines which kernel thread a kernel process should use, since the threads are contending for the processor.

When we say the thread library schedules user threads onto available LWPs, we do not mean that the thread is actually running on a CPU; this would require the OS to schedule the kernel thread onto a physical CPU. To decide which kernel thread to schedule onto a CPU, the kernel uses System Contention Scope