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MPI One-sided communications have the potential to increase applications performance by reducing the noise on remote processors. They consist in Remote Memory Accesses roughly orchestrated in two types of operations: memory synchronizations and actual RMAs. Applications such as PGAS ones benefit from RMAs operations, yet they require to get notified when such a communication has completed in order to process the data. Using heavy provided synchronization mechanisms for each communication impact performance drastically. One of the solutions is for applications to implement a notification mechanism through a supplementary communication. To alleviate the need for developers to manage this notification mechanism, we propose an extension to the MPI one-sided API that provides RMAs with accompanying notification. We present a basic implementation of this extension that relies solely on existing MPI one-sided communications and provide all the functionality, that can be ported to any MPI libraries for their supported networks. We also propose an implementation targeting performance in Open MPI over InfiniBand's network, and present its performance evaluation. |
