| Issue |
EPJ Web of Conf.
Volume 295, 2024
26th International Conference on Computing in High Energy and Nuclear Physics (CHEP 2023)
|
|
|---|---|---|
| Article Number | 02007 | |
| Number of page(s) | 8 | |
| Section | Online Computing | |
| DOI | https://doi.org/10.1051/epjconf/202429502007 | |
| Published online | 06 May 2024 | |
https://doi.org/10.1051/epjconf/202429502007
Commissioning of the ALICE readout software for LHC Run 3
CERN – European Organisation for Nuclear Research, Geneva, Switzerland
* Corresponding author: sylvain.chapeland@cern.ch
Published online: 6 May 2024
ALICE (A Large Ion Collider Experiment) is a heavy-ion detector studying the physics of strongly interacting matter and the quarkgluon plasma at the CERN LHC (Large Hadron Collider). During the second long shut-down of the LHC, the ALICE detector was upgraded to cope with an interaction rate of 50 kHz in Pb-Pb collisions, producing in the online computing system (O2) a sustained input throughput of 3.5 TB/s.
In the past years, the O2/FLP project built the new data-acquisition system capable of handling this load. It consists of 200 readout nodes, collecting the data transferred from over 8000 detector links to PCs memory by dedicated PCI boards. The readout software manages the hardware and software memory buffers used for DMA and inter-process communication. It initiates the data flow, performs on-the-fly consistency checks, formats the data, reports performance, and finally pushes the data to the local processing pipeline. The output is then sent by the data distribution software over 100Gb/s links to a dedicated event processing farm.
The readout software modular design allowed to address the manifold needs faced during the prototyping, installation and commissioning phases, which proved essential from the lab tests to physics production, like file replay and recording, or online multi-threaded LZ4 compression.
We will describe the hardware and software implementation of the O2 readout system, and review the challenges met during the commissioning and first months of operation with LHC collisions in 2022.
© The Authors, published by EDP Sciences, 2024
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.
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