Section: New Results

Description, Implementation and Evaluation of an Affinity Clause for Task Directives

Participants : Philippe Virouleau, Adrien Roussel [IFPEN] , François Broquedis, Thierry Gautier [Inria, AVALON] , Fabrice Rastello, Jean-Marc Gratien [IFPEN] .

This work extends the affinity-based scheduling we proposed at the Europar 2016 conference to fit the philosophy of OpenMP programming. On this topic, OpenMP does not provide a lot of flexibility to the programmer yet, which lets the runtime system decide where a task should be executed. In this work, we propose our own interpretation of the new affinity clause for the task directive, which is being discussed by the OpenMP Architecture Review Board. This clause enables the programmer to give hints to the runtime about tasks placement during the program execution, which can be used to control the data mapping on the architecture. In our proposal, the programmer can express affinity between a task and the following resources: a thread, a NUMA node, and a data. We provide an implementation of this proposal in the Clang-3.8 compiler, and an implementation of the corresponding extensions in the xkaapi OpenMP runtime system.

This work has been presented at the international workshop on OpenMP IWOMP'2016 [23].