In this paper, we discuss the spectrum management technologies including spectrum sensing, spectrum decision, spectrum sharing, and spectrum handoff schemes in cognitive radio (CR) networks. In order to evaluate performance of different spectrum management schemes, the preemptive resume priority (PRP) M/G/1 queuing model is suggested to characterize the spectrum usage behavior between the primary and the secondary users. Based on this model, we derive a new performance measure - the overall system time of the secondary connections. The overall system time is an important performance measure to provide the quality of service (QoS) provisioning service for the secondary users. It is defined as the duration from the instant that data arrives at system until the instant of finishing the whole transmission. Clearly, multiple interruptions from the high-priority primary users will increase the overall system time of the low-priority secondary users. Based on the PRP M/G/1 queuing model, the impacts of multiple interruptions on the overall system time can be evaluated. On top of this model, a spectrum sensing, a spectrum decision, a spectrum sharing, and a spectrum handoff algorithms are investigated to reduce the overall system time. From the numerical results, we can design better spectrum management policies to satisfy the QoS requirement of the secondary users in CR networks and provide useful insight into the design tradeoff for different spectrum management technologies.