Speaker
Description
ALICE (A Large Ion Collider Experiment) is a heavy-ion detector studying the physics of
strongly interacting matter and the quark-gluon plasma at the CERN LHC (Large Hadron
Collider). During the second long shut-down of the LHC, the ALICE detector will be
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 TB/s.
The readout software is in charge of the first step of data-acquisition, handling the
data transferred from over 8000 detector links to PCs memory by dedicated PCI boards,
formatting and buffering incoming traffic until sent to the next components in the
processing pipeline. On the 250 readout nodes where it runs, it has to sustain a
throughput which can locally exceed 100 Gb/s.
We present the modular design used to cope with various data sources (hardware devices
and software emulators), integrated with the central O2 components (logging,
configuration, monitoring, data sampling, transport) and initiating the online data flow
using the standard O2 messaging system. Performance considerations and measurements are
also discussed.
