Speaker
Description
CBM is a heavy-ion experiment at the future FAIR facility in
Darmstadt, Germany. Featuring self-triggered front-end electronics and
free-streaming read-out event selection will exclusively be done by
the First Level Event Selector (FLES). Designed as an HPC cluster,
its task is an online analysis and selection of
the physics data at a total input data rate exceeding 1 TByte/s. To
allow efficient event selection, the FLES performs timeslice building,
which combines the data from all given input links to self-contained,
overlapping processing intervals and distributes them to compute
nodes. Partitioning the input data streams into specialized containers
allows this task to be performed very efficiently.
The FLES Input Interface defines the linkage between the FEE and the
FLES data transport framework. A custom FPGA PCIe board, the FLES
Interface Board (FLIB), is used to receive data via optical links and
transfer them via DMA to the host's memory. The current prototype of
the FLIB features a Kintex-7 FPGA and provides up to eight 10 GBit/s
optical links. A custom FPGA design has been developed for this
board. DMA transfers and data structures are optimized for subsequent
timeslice building. Index tables generated by the FPGA enable fast
random access to the written data containers. In addition the DMA
target buffers can directly serve as InfiniBand RDMA source buffers
without copying the data. The usage of POSIX shared memory for these
buffers allows data access from multiple processes. An accompanying
HDL module has been developed to integrate the FLES link into the
front-end FPGA designs. It implements the front-end logic interface as
well as the link protocol.
Prototypes of all Input Interface components have been implemented and
integrated into the FLES test framework. This allows the
implementation and evaluation of the foreseen CBM read-out chain. The
full chain from FEE up to timeslices has been tested
successfully. Setups with 16 and more free-streaming input links will
be used for upcoming beam tests. An overview of the FLES Input
Interface as well as latest results from performance and stability
measurements will be presented.
| Primary Keyword (Mandatory) | DAQ |
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