Improving Scalability of Processor Utilization on Heavily-Loaded Servers with Real-Time Scheduling

E. Kawai, Y. Kadobayashi, and S. Yamaguchi (Japan)


polling I/O, interval control, real-time scheduling, select(), poll(), server performance


It is a well-known issue that the polling I/O, such as select() and poll(), has a poor scalability. As a so lution of the problem, we previously proposed the inter val control technique of the polling I/O, which eases exces sively frequent invocations of the polling I/O [1]. Although the benchmark tests proved that the technique effectively reduced the service latency, it still has a problem of high processor usage when the number of concurrent sockets grows large. This problem is caused by unexpected context switches, which degrade the efficacy of the interval control. In this paper, we propose the interval control technique with POSIX real-time scheduling that prevents such unexpected interruptions. Because programs under real-time schedul ing are difficult to develop and they often cause a system wide freeze, simple application of real-time scheduling to the interval control mechanism is considered.

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