White Papers

Figure 7: Comparing snoop modes and BIOS Profiles for OpenFOAM Motorbike 11M benchmark
For the openFOAM motorbike 11M benchmark the OSB, COD and the HS snoop modes perform similarly with about
1% variation. The performance for ES is low across all the processor models and it keeps on dropping as the number
of cores increase as shown in the left graph of figure 7. The snoop modes with BIOS System Profile set to
Performance follow exactly similar trend. As shown in the right graph on figure 3, the DAPC and Performance profiles
show similar performance with Performance about 1% better in most cases except for the E5-2697A where the
DAPC.COD was 2% better.
Conclusion
Most of the data sets used in this study show advantage of COD mode, but COD benefits codes which are highly
NUMA optimized and where the dataset fit into the NUMA memory (that is half of each sockets memory capacity).
OSB is a close second and a good option for codes with varying level of NUMA optimization; OSB is also the default
memory snoop BIOS option. HS and ES perform slightly lower than COD and OSB. ES is better than HS for lower
core counts but as the core counts increase ES starts paying the penalty of having lower request tokens per core for
higher core counts compared to the other snoop modes. In terms of System Profile, Performance Profile performs
slightly better than DAPC in most of the cases.
Be sure to check back next week for the last blog in the series which will compare the performance of HPC CAE
applications across generations (Ivy-bridge vs. Haswell vs. Broadwell)
