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Transition to a new CPU benchmark

This document discusses the transition to a new CPU benchmarking unit and the adoption of the SPECall_cpp2006 benchmark. It also includes the results of benchmarking on the LXBENCH cluster at CERN and proposes a conversion factor for the new CPU unit. The transition period and the recalibration of requirements tables and pledges are also addressed.

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Transition to a new CPU benchmark

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  1. Transition to a new CPU benchmark G. Merino, GDB 14 Jan 2008 • on behalf of the “GDB benchmarking WG”: • HEPIX: Manfred Alef, Helge Meinhard, Michelle Michelotto • Experiments: Peter Hristov, Alessandro De Salvo and Franco Brasolin, Marie-Christine Sawley, Hubert Degaudenzi • Chair: Gonzalo Merino

  2. Background • July 2008: The HEPIX CPU WG recommended the MB to adopt SPECall_cpp2006 as new benchmark. • Document describing the new benchmark chosen and the conditions in which it will have to be run is in preparation by the HEPIX WG. • Mandate of our Working Group: • Publish the recipe for running the benchmark (see above) • Agree on conversion factors to convert experiment requirement and site pledges tables from si2k units to the new units • Aim of this talk is not to present a formal proposal, but to report on the Group discussions up to now and get reactions/feedback.

  3. LXBENCH cluster at CERN • Cluster with 8 reference machines for benchmarking at CERN: • lxbench01, lxbench02, … lxbench08 • (see https://twiki.cern.ch/twiki/bin/view/FIOgroup/TsiLxbench) • Old (SPECint2000) and new (SPECall_cpp2006) benchmarks have been run in every machine. • Experiments also ran their apps in every machine (May-08, HEPIX CPU WG) • Conclusion: All 4 experiments see good correlation between their applications and both benchmarks. • NOTE: Not all the experiments ran in lxbench08 • Only ATLAS managed to run and provide results for lxbench08 • LHCb says it did run, but results still not provided to the HEPIX group • CMS and ALICE did not manage to run in lxbench08 in May

  4. SPECs on LXBENCH

  5. Current processors at the T0/T1s Xeon E5345 (Quad-core) Xeon E5430 (Quad-core) AMD Intel Dual-Core Quad-Core Result of a poll the Tier-0 and Tier-1s showing a snapshot of the number of cores currently installed of each processor type

  6. Transition to a new CPU unit • The most representative platform, providing the majority of capacity at T0/T1s today are the Intel QuadCore processors. • Propose to focus on the conversion factor results got at the newest (Intel QuadCore) machines: lxbench07 and lxbench08 • lxbench07: 4,05 • lxbench08: 3,84 • Manfred Alef did the exercise of computing the CPU performance delivered by the whole GridKa farm with both the old and the new SPEC benchmarks • large site with quite a lot of different processors  realistic “mixture” • Result: new/old conversion factor = 4,19 • Precision O(5%) intrinsic to these measurements: not significative.

  7. Transition to a new CPU unit • Proposal: Take a simple approach and adopt 4,00 as conversion factor.  • Give more importance to having a simple rule for the transition period than discussing about decimals within the 5% precision. • Caveat: during the next days, ALICE and CMS will complete their benchmarking runs up to lxbench08 to confirm the good correlation (no surprises expected). • Transition period: before end April (Spring C-RRB meeting) • Experiments will re-compute requirements tables given the new LHC schedule: new numbers should be computed already with the new unit. • Sites should buy SPECcpu2006 and calibrate their farms to report their current CPU power in the new unit. Pledges for the Spring CRRB should be expressed in the new unit.

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