本文对 epoll、select 和 poll 的效率作了详细的测评和比较。

Comparing and Evaluating epoll, select, and poll Event Mechanisms

Abstract

This paper uses a high-performance, event-driven, HTTP server (the ¦Ìserver) to compare the performance of the select, poll, and epoll event mechanisms. We subject the ¦Ìserver to a variety of workloads that allow us to expose the relative strengths and weaknesses of each event mechanism. Interestingly, initial results show that the select and poll event mechanisms perform comparably to the epoll event mechanism in the absence of idle connections. Profiling data shows a significant amount of time spent executing a large number of epoll_ctl system calls. As a result, we examine a variety of techniques for reducing epoll_ctl overhead including edge-triggered notification,and introducing a new system call (epoll_ctlv) that aggregates several epoll_ctl calls into a single call. Our experiments indicate that although these techniques are successful at reducing epoll_ctl overhead, they only improveperformance slightly.

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