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CRU data format

CRU data format. ALICE O 2 -CRU. SPOILER ALERT. CRU team would keep the word padding and these are the reasons …. DATA FORMAT (RAW MODE). GBT MODE 37.5% extra padding. 48 bit. 80 bit. WIDE MODE 12.5% extra padding. 16 bit. 112 bit. DATA FORMAT (DET User Logic). 128 bit. DET UL

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CRU data format

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  1. CRU data format ALICE O2-CRU

  2. SPOILER ALERT CRU team would keep the word padding and these are the reasons …

  3. DATA FORMAT (RAW MODE) GBT MODE 37.5% extra padding 48 bit 80 bit WIDE MODE 12.5% extra padding 16 bit 112 bit

  4. DATA FORMAT (DET User Logic) 128 bit DET UL 0% extra padding

  5. Experiment THROUGHPUT

  6. Experiment THROUGHPUT TPC generates 90% of the total throughput in ALICE

  7. DET CRU/FLP

  8. DET User Logic CRU DET UL = 430 (TOT 473) = 90 % no memory loss FLP UL = 215 (TOT 247) = 87 % no memory loss

  9. TPC RAW MODE GBT WORD 112 bit Throughput 112 bit @ 40 MHz = 4.48 Gb/s 20 GBT link x CRU = 89.6 Gb/s 100 us @ 10 Hz = 90 Mb/s Extra padding GBT WORD 128 bit Throughput 128 bit @ 40 MHz = 5.12 Gb/s 20 GBT link x CRU = 102.4 Gb/s 100 us @ 10 Hz = 100 Mb/s 2 CRU x FLP = 200 Mb/s 3 CRU x FLP = 300 Mb/s

  10. CONCLUSIONS • During PHYSICS data taking the UL is used, so no extra padding in 90% of the CRU • When the RAW mode is used the extra padding is added, however in this case we run in trigger or throttling mode. We lose the 12.5 % of memory for limited amount of data (requirement for DEBUG/CALIBRATION mode is 100 Mb/s) • DETECTOR that will have always the padding in place are ITS, MFT, TOF. Their contribution in terms of data throughput is < 60 GB/s. • The work to change the data format is not trivial: • consequence in the firmware, more complexity and this is for 3 different type of usage wide continuous, GBT continuous and GBT packets (3 different packers and size computer), • consequence in the software, data are not easily readable anymore, even for CRU tests, • the modification will affect all the CRUs but only a 10% will actually benefit from it (the ones that don’t have DET UL). • http://svnweb.cern.ch/world/wsvn/alicetdrrun3/Notes/Run34SystemNote/detector-read-alice/ALICErun34_readout.pdf

  11. QUESTIONS • How the extra padding affect the reconstruction in terms of computing power? • The TPC will have local processing in the FLP anyway. If the extra padding is an issue when running in DEBUG mode, it could be removed by a software before shipping the data over the network. • What is the amount of DATA that the experiment will collect in DEBUG mode over the year compared to PHYSICS DATA?

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