Asynchronous programming models (APM) are gaining more and more traction, allowing applications to expose the available concurrency to a runtime system tasked with coordinating the execution. While MPI has long provided support for multi-threaded communication and non-blocking operations, it falls short of adequately supporting APMs as correctly and efficiently handling MPI communication in different models is still a challenge. We have previously proposed an extension to the MPI standard providing operation completion notifications using callbacks, so-called MPI Continuations. This interface is flexible enough to accommodate a wide range of different APMs.

In this paper, we present an extension to the previously described interface that allows for finer control of the behavior of the MPI Continuations interface. We then present some of our first experiences in using the interface in the context of different applications, including the NAS parallel benchmarks, the PaRSEC task-based runtime system, and a load-balancing scheme within an adaptive mesh refinement solver called ExaHyPE. We show that the interface, implemented inside Open MPI, enables low-latency, high-throughput completion notifications that outperform solutions implemented in the application space.

异步编程模型（APM）越来越受到青睐，允许应用程序将可用的并发公开给负责协调执行的运行时系统。虽然MPI长期以来一直提供对多线程通信和非阻塞操作的支持，但由于无法正确地，有效地处理不同模型中的MPI通信仍然是一个挑战，因此它不足以充分支持APM。我们之前已经提出了MPI标准的扩展，该标准提供了使用回调的操作完成通知，即所谓的MPI Continuations。该接口足够灵活，可以容纳各种不同的APM。

在本文中，我们提出了对先前描述的接口的扩展，该接口允许对MPI Continuations接口的行为进行更好的控制。然后，我们介绍在不同应用程序上下文中使用接口的一些初步经验，包括NAS并行基准测试，基于PaRSEC任务的运行时系统，以及在称为ExaHyPE的自适应网格细化求解器中的负载平衡方案。我们展示了在Open MPI内部实现的接口可以实现低延迟，高吞吐量的完成通知，其性能优于在应用程序空间中实现的解决方案。