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
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 SPECall_cpp2006 (new) KSI2K-LCG (old) Ratio new/old
Intel Xeon 2.8 GHz
lxbench01
10,24
2,25
4,55
lxbench02
9,63
2,24
4,29
AMD Opteron 275
lxbench03
28,03
6,20
4,52
Intel Xeon 5150
lxbench04
35,58
8,51
4,18
Intel Xeon 5160
lxbench05
38,21
9,27
4,12
AMD Opteron 2218
lxbench06
31,67
6,85
4,62
Intel Xeon E5345
lxbench07
57,52
14,19
4,05
Intel Xeon E5410
lxbench08
60,76
15,83
3,84

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

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.