The preemptible method changes the kernel into preemptible kernel by modifying the interrupted handling and spinlock mechanism,while the low-latency method makes the kernel to execute other tasks by adding the scheduling point into long period tasks.

6,this paper analyzes strategies in scheduling time,scheduling policy,and kernel preemption first introduced by kernel 2.

Especially the importation of new scheduler,preemptive kernel and O(1) scheduling algorithm improve the real-time performance of Linux greatly.

The importance of preemptive kernel mechanism for a hard-realtime measurement and control application is explained by analysing preemption latency of process in a realtime operating system.

4 kernel in supporting the real-time process with POSIX compliant real-time function,multithread,multitasks,preemptive kernel, O(1)scheduling algorithm,its real-time capability is very poor and can not ensure the response time of real-time task.