CPU Scheduler Selects from among the processes in memory that are ready to execute, and allocates the cpu to one of them.(选择内存 中的就绪进程,并分配cPU给其中之一) CPU scheduling decisions may take place when a process (cPU调度可能发生在当一个进程): 1. Switches from running to waiting state(从运行转到等待) 2 Switches from running to ready state(从运行转到就绪) 3 Switches from waiting to ready(从等待转到就绪) 4. Terminates(终止运行) Scheduling under1and4 is nonpreemptive(发生在1、4两 种情况下的调度称为非抢占式调度) All other scheduling is preemptive(其他情况下发生的调度称 为抢占式调度) Applied Operating System Concepts 6.5 Silberschatz, Galvin, and Gagne @19996.5 Silberschatz, Galvin, and Gagne ©1999 Applied Operating System Concepts CPU Scheduler • Selects from among the processes in memory that are ready to execute, and allocates the CPU to one of them.（选择内存 中的就绪进程，并分配CPU给其中之一） • CPU scheduling decisions may take place when a process （CPU调度可能发生在当一个进程）: 1. Switches from running to waiting state（从运行转到等待）. 2. Switches from running to ready state（从运行转到就绪）. 3. Switches from waiting to ready（从等待转到就绪）. 4. Terminates（终止运行）. • Scheduling under 1 and 4 is nonpreemptive （发生在1、4两 种情况下的调度称为非抢占式调度）. • All other scheduling is preemptive （其他情况下发生的调度称 为抢占式调度）