Soft timers: efficient microsecond software timer support for network processing

TLDR: This paper proposes and evaluates soft timers, a new operating system facility that allows the efficient scheduling of software events at agranularity down to tens of microseconds, and shows that this technique can improve the throughput of a Web server by up to 25%.

Abstract: This paper proposes and evaluates soft timers, a new operating system facility that allows the efficient scheduling of software events at agranularity down to tens of microseconds. Soft timers can be used to avoid interrupts and reduce context switches associated with network processing, without sacrificing low communication delays. More specifically, soft timers enable transport protocols like TCP to efficiently perform rate-based clocking of packet transmissions. Experiments indicate that soft timers allow a server to employ rate-based clocking with little CPU overhead (2-6%) at high aggregate bandwidths. Soft timers can also be used to perform network polling, which eliminates network interrupts and increases the memory access locality of the network subsystem without sacrificing delay. Experiments show that this technique can improve the throughput of a Web server by up to 25%.