Phoronix article – POWER9, Xeon and AMD comparison (2018-06-25)
Phoronix posted an article comparing POWER vs x86 on CPU benchmarks. This post looks at some of the workloads and adds comments.
I don’t have a POWER9 system and haven’t run these on a server. However, I’ve run the workloads on AMD (Ryzen) and Intel (Haswell) clients and made some observations. Details in the table below.
Also a few overall comments:
- x264 likely has tuned x86 assembly
- compress-zstd is single-threaded on x86 and much faster on POWER9, is there something else going on
- single-threaded benchmarks aren’t differentiated as much in the article, e.g. price/performance of phpbench a bit strange
| Benchmark | Phoronix observations | My observations | Analysis |
|---|---|---|---|
| parboil: LBM | EPYX 7401P and 7601 slightly faster than 18-core power. | LBM: OpenMP program with 95% On_CPU. IPC of 1.15 with more frontend stalls than backend. | Analysis |
| x264 | POWER9 system quite a bit slower than corresponding x86 systems. | On_CPU 71%, many voluntary context switches and I/O read input. IPC 1.3 | Analysis |
| compress-p7zip | POWER9 system slightly faster than EPYC 7601 and 7401 | On_CPU 88% with some I/O to limit scaling. IPC 0.83 with 27% speculation misses (branch prediction). | Analysis |
| stockfish | POWER9 system faster than EPYC 7401P and slower than EPYC 7601 | On_CPU 100%, IPC of 1.0 with frontend stalls and bad speculation. | Analysis |
| build-llvm | POWER9 system faster than EPYC 7401P and slower than EPYC 7601 | On_CPU 99% much higher than other build-* benchmarks. High amount of frontend stalls. Some speculative misses due to branch prediction. Overall IPC on low side of 0.64. Technically speaking different workloads since one builds an x86 executable and the other a POWER executable. | Analysis |
| primesieve | POWER9 system slower than EPYX 7401P and 7601 | On_CPU almost 100%. Backend stalls are largest issue but overall IPC is 0.69. | Analysis |
| compress-zstd | POWER9 system fastest overall, EPYC slowest, Intel in between | Single-threaded benchmark (compress-zstd seems to use multiple threads), with a high level of backend stalls. | Analysis |
| encode-flac | POWER9 system slowest overall, much slower than EPYC | Single threaded with On_Core 90%. Some I/O more writes than reads. IPC 2.43 with 27% backend stalls. L2 miss ratio 20% and L3 6%. | Analysis |
| encode-mp3 | POWER9 system slowest overall much slower than EPYC | Single threaded with On_core of 100%. IPC of 1.90. 35% backend stalls with L2 miss ratio 47% and L3 miss ratio 6%. | Analysis |
| openssl | POWER9 system slightly faster than EPYX 7401P and slower than EPYC 7601 | On_CPU 100% with IPC 1.66 (Intel) vs 1.12 (AMD) appears related to hand-coded assembly with MULX instructions. High retirement rate of 90%. | Analysis |
| pgbench | POWER9 system faster than EPYC on read-only and read-write, closer on the latter | PostgreSQL database and frontend driver with multiple options. Read keeps cores busier than read/write but light usage overage - at least as much latency issues. Frontend stalls are the largest issues, e.g. icache. | Analysis |
| pybench | POWER9 system slightly slower on pybench | Single threaded micro-benchmarks of different python operations. IPC over 2.5 with frontend stalls the largest issue. | Analysis |
| phpbench | POWER9 system slightly faster than EPYC 7601. | Single threaded, micro-benchmarks of php operations. IPC of 2.76 with ~15% of frontend stalls and ~15% of backend stalls. | Analysis |
| scikit-learn | POWER9 system slower than EPYC systems by reasonable amount. | Single threaded, python code. High IPC with some backend memory stalls. | Analysis |
| tinymembench | POWER9 system slightly slower than EPYC | Backend bound, IPC 0.4, testing memory performance and 90% backend stalls. | Analysis |
| blender: classroom, pabellion barcelona | POWER9 system somewhat slower than EPYC | On_CPU close to 100% with ~20% stalls in backend and ~20% stalls in front end and bad speculation of ~10%. An overall IPC of 0.80 | Analysis |
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