基于接纳时间比控制和比例积分调节器的接纳控制机制

讨论电子商务网站的过载保护问题，给出了一种基于接纳时间比控制和比例积分调节器的接纳控制(admission control)机制.该机制运用PI调节器，动态调整控制周期中服务器接纳请求的时间长度，主动拒绝过量请求，实现接纳控制.实验表明，基于接纳时间比的反馈控制机制即使在严重过载时，仍能使服务器的实际负载与最大处理能力接近，其吞吐率和响应时间均与服务器满载时相当；此外，仿真还表明这一机制能有效地实现资源控制和服务质量控制.

Enforcing Admission Control Using Admission-Time-Ratio and PI Controller

In this paper a session-based admission time-ratio feedback control mechanism is presented for improving the Web QoS of commercial applications. The mechanism combines a novel session-based admission control (AC) policy with a PI controller. The admission control strategy manages the amount of requests that the server can accept, by dynamically changing the admitting time interval in the control period. During the admitting time interval all requests are admitted. The admission time ratio is naturally defined as the ratio of the admitting time interval in the control period. The novel admission control mechanism is agile and more easily implemented than adjusting the queue length. Moreover, PI controller designed using system identification and control theory makes this scheme robust and auto-tunable. The simulation results of Tomcat server provided in the paper demonstrate that it can improve the performance effectively and ease the resource control and QoS control.