Assessing Cavium's ThunderX2: The Arm Server Dream Realized At Last
by Johan De Gelas on May 23, 2018 9:00 AM EST- Posted in
- CPUs
- Arm
- Enterprise
- SoCs
- Enterprise CPUs
- ARMv8
- Cavium
- ThunderX
- ThunderX2
SPEC CPU2006 Cont: Per-Core Performance w/SMT
Moving beyond single-threaded performance, multi-threaded performance within the confines of a single core is of course also important. The Vulcan CPU architecture was designed from the start to leverage SMT4 to keep its cores occupied and boost their overall throughput, so this is where we'll look next.
| SPEC CPU2006: Single Core w/SMT | ||||||
| Subtest SPEC CPU2006 Integer |
Application Type | Cavium ThunderX 2 GHz gcc 5.2 1 thread |
Cavium ThunderX2 @2.5 GHz gcc 7.2 4 threads |
Xeon 8176 @3.8 GHz gcc 7.2 2 threads |
Thunder X2 vs Xeon 8176 |
Thunder X2 vs ThunderX |
| 400.perlbench | Spam filter | 8.3 | 24.1 | 50.6 | 48% | 290% |
| 401.bzip2 | Compression | 6.5 | 22.9 | 31.9 | 72% | 350% |
| 403.gcc | Compiling | 10.8 | 35 | 38.1 | 92% | 330% |
| 429.mcf | Vehicle scheduling | 10.2 | 52.4 | 50.6 | 104% | 510% |
| 445.gobmk | Game AI | 9.2 | 25.1 | 35.6 | 71% | 270% |
| 456.hmmer | Protein seq. analyses | 4.8 | 26.7 | 41 | 65% | 560% |
| 458.sjeng | Chess | 8.8 | 22.4 | 37.1 | 60% | 250% |
| 462.libquantum | Quantum sim | 5.8 | 83.6 | 83.2 | 100% | 1440% |
| 464.h264ref | Video encoding | 11.9 | 34 | 66.8 | 51% | 290% |
| 471.omnetpp | Network sim | 7.3 | 31.1 | 41.1 | 76% | 440% |
| 473.astar | Pathfinding | 7.9 | 27.2 | 33.8 | 80% | 340% |
| 483.xalancbmk | XML processing | 8.4 | 33.8 | 75.3 | 45% | 400% |
First of all, the ThunderX2 core is a massive improvement over the simple ThunderX core. Even excluding libquantum – that benchmark could easily run 3 times faster on the older ThunderX core after some optimization and compiler improvements – the new ThunderX2 is no less than 3.7 times faster than its older brother. This kind of an IPC advantage makes the original ThunderX's 50% core advantage all but irrelevant.
Looking at the impact of SMT, on average, we see that 4-way SMT improves the ThunderX2's performance by 32%. This ranges from 8% for video encoding to 74% for pathfinding. Intel meanwhile gets a 18% boost from their 2-way SMT, ranging from 4% to 37% in the same respective scenarios.
Overall, a boost of 32% for the ThunderX2 is decent. But it does invite an obvious comparison: how does it fare relative to another SMT4 architecture? Looking at IBM's POWER8, which also supports SMT4, at first glance there seems to be some room for improvement, as the POWER8 sees a 76% boost in the same scenario.
However this isn't entirely an apples-to-apples comparison, as the IBM chip had a much wider back-end: it could issue 10 instructions while the ThunderX2 core is limited to 6 instructions per cycle. The POWER8 core was also much more power hungry: it could fit only 10 of those ultra-wide cores inside a 190W power budget on a 22 nm process. In other words, further increasing the performance gains from using SMT4 would likely require even wider cores, and in turn seriously impact the total number of cores available inside the ThunderX2. Still, it is interesting to put that 32% number into perspective.
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DrizztVD - Wednesday, May 23, 2018 - link
It amazes me how the one big advantage ARM could have is the power efficiency, yet no power efficiency numbers in this review? It's like someone just isn't thinking about what can best showcase the ARM advantage and testing it.boeush - Thursday, May 24, 2018 - link
You must have missed this bit:"So as is typically the case for early test systems, we are not able to do any accurate power comparisons.
In fact, Cavium claims that the actual systems from HP, Gigabyte and others will be far more power efficient."
This was an early (and apparently quite buggy, especially from the power management standpoint) test system. It's not representative of final production systems in these respects, so doing what you request on it would only put a very crude lower bound on efficiency, at best.
That's why the final section of the write-up has a title ending in ": so far"... (obviously, there will be more to come if/when real production-quality systems are available for benchmarking/analysis.)
ZolaIII - Thursday, May 24, 2018 - link
It's broken currently on the MB. If you want to see real power/performance metrics for a SoC made on comparable lithography to the lintels 14 nm (aka TSMC 10nm) & with optimised software read this:https://blog.cloudflare.com/neon-is-the-new-black/
drwho9437 - Wednesday, May 23, 2018 - link
Thanks Johan, I've been reading since Ace's. I can't believe it has been more almost 20 years. Even though I don't work in this market I still read everything you write.JohanAnandtech - Friday, May 25, 2018 - link
It was indeed almost 20 years ago that I published my first article about the K6-2 vs Pentium MMX. And Anand's star was about to rise with the launch of the K6-3 :-).Spatz - Wednesday, May 30, 2018 - link
Wow. Aces hardware... that used to be my go to for hardware reviews back in the day. I can’t believe your still at it! This article was great. Keep up the good work.beginner99 - Thursday, May 24, 2018 - link
So it for sure is an option. however I d not get the focus on price. The CPU cost is a small fraction of the total server cost and a tiny if infrastructure cost (network, HVAC,...) is included. Add to that the software and data running on that server and if your CPU is 5% faster at same power it costing $5000 more might be totally worth it.Apple Worshipper - Thursday, May 24, 2018 - link
Errmm... does ARM feature SMT now?Ryan Smith - Thursday, May 24, 2018 - link
Not in Arm's own cores. But in Cavium's ThunderX2, yes.sgeocla - Thursday, May 24, 2018 - link
What's up with EPYC comparison missing in almost all benchmarks?EPYC has been out for a while and the only benchmarks are from almost a year ago?