CERN Accelerating science

ATLAS Slides
Report number	ATL-DAQ-SLIDE-2020-336
Title	Preparing the ATLAS Trigger Software for Multi-threaded Operation
Author(s)	Stockton, Mark (European Laboratory for Particle Physics, CERN) ; ATLAS Collaboration
Corporate author(s)	The ATLAS collaboration
Collaboration	ATLAS Collaboration
Submitted to	40th International Conference on High Energy Physics (ICHEP), Prague, Czech Republic, 28 Jul - 6 Aug 2020
Submitted by	[email protected] on 26 Aug 2020
Subject category	Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN LHC ; ATLAS
Free keywords	Trigger ; HLT ; AthenaMT ; multi-threaded
Abstract	Athena is the software framework used in the ATLAS experiment throughout the data processing path, from the software trigger system through offline event reconstruction to physics analysis. The shift from high-power single-core CPUs to multi-core systems in the computing market means that the throughput capabilities of the framework have become limited by the available memory per process. For Run 2 of the Large Hadron Collider (LHC), ATLAS has exploited a multi-process forking approach with the copy-on-write mechanism to reduce the memory use. To better match the increasing CPU core count and the, therefore, decreasing available memory per core, a multi-threaded framework, AthenaMT, has been designed and is now being implemented. The ATLAS High Level Trigger (HLT) system has been remodelled to fit the new framework and to rely on common solutions between online and offline software to a greater extent than in Run 2. We present the implementation of the new HLT system within AthenaMT, which is being commissioned now for ATLAS data-taking during LHC Run 3 (2021 onwards).