https://doi.org/10.1051/epjconf/201921405017
I/O in the ATLAS multithreaded framework
1 Argonne National Laboratory,
9700 S Cass Ave
Argonne
IL 60439
2
Brookhaven National Laboratory,
Upton
NY 11973
* e-mail: cranshaw@anl.gov
Published online: 17 September 2019
Scalable multithreading poses challenges to I/O for the ATLAS experiment. The performance of a thread-safe I/O strategy may depend upon many factors, including I/O latencies, whether tasks are CPU- or I/O-intensive, and thread count. In a multithreaded framework, an I/O infrastructure must efficiently supply event data to and collect it from many threads processing multiple events in flight. In particular, on-demand reading from multiple threads may challenge caching strategies that were developed for serial processing and may need to be enhanced. This I/O infrastructure must also address how to read, make available, and propagate in-file metadata and other non-event data needed as context for event processing. We describe the design and scheduling of I/O components in the ATLAS multithreaded control framework, AthenaMT, for both event and non-event I/O. We discuss issues associated with exploiting the multithreading capabilities of our underlying persistence technology, ROOT, in a manner harmonious with the ATLAS framework?s own approach to thread management. Finally, we discuss opportunities for evolution and simplification of I/O components that have successfully supported ATLAS event processing for many years from their serial incarnations to their thread-safe counterparts.
© The Authors, published by EDP Sciences, 2019
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
