Single-threaded Integer Performance: 7-Zip

The profile of a compression algorithm is somewhat similar to many server workloads: it can be hard to extract instruction level parallelism (ILP) and it's sensitive to memory parallelism and latency. The instruction mix is a bit different, but it's still somewhat similar to many server workloads. Testing single threaded is also a great way to check how well the turbo boost feature works in a CPU.

And as one more reason to test performance in this manner, the 7-zip source code is available under the GNU LGPL license. That allows us to recompile the source code on every machine with the -O2 optimization with gcc 4.8.2.

We added the 7-zip scores that we could find at the 7-zip benchmark page. But there is more. The numbers on the 7-zip bench page have no software details, so we could not be sure that they would be accurate. So we managed to get a brief session on a POWER8 "for development purposes" server. The hardware specs can be read below:

Yes, we only got access to 1 core (8 threads) and 2 GB of RAM. So real world server benchmarking was out of the question. Nevertheless, it's a start. To that end we tested with gcc 4.9.1 (supports POWER8) and recompiled our source with the "-O2 -mtune="power8" options on Ubuntu Linux 14.10 for POWER. 

LZMA Single-Threaded Performance: Compression

Let us first focus on the new Haswell core inside the Xeon E7, which offers a solid 10% improvement. Turbo boost brings the clockspeed of the Haswell core close enough to the Ivy Bridge core (3.3GHz vs 3.4GHz) and the improved core does the rest. Nevertheless, it is clear that we should not expect huge performance increases with a 10% faster core and 20% more cores.

Back to the more exciting stuff: the fight between Intel and IBM, between the Xeon "Haswell" and the POWER8 chip. The Haswell core is a lot more sophisticated: single threaded performance at 3.3 GHz (turbo) is no less than 50% higher than the POWER8 at 3.4 GHz. That means that the Haswell core is a lot more capable when it comes to extracting ILP out of that complex code.

However, when the IBM monster is allowed to use 8 simultaneous threads spread out over one core, something magical happens. Something that we have not seen in a long, long time: the Intel chip is no longer on top. When you use all the available threading resources in one core, the 3.4 GHz chip is a tiny bit (2%) faster than the best Intel Xeon at 3.3 GHz.

Memory Subsystem: Bandwidth 7-Zip Decompression
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  • Brutalizer - Tuesday, May 12, 2015 - link

    Again, Hana is a clustered RAM database. And as I have shown above with the Oracle TenTimes RAM database, these are totally different from a normal database. In Memory DataBases can never replace a normal database, as IMDB are optimized for reading data (analysis), not modifying data.

    Regarding SGI UV300H, it is a 16 socket server, i.e. scale-up server. It is not a huge scale-out cluster. And therefore UV300H might be good for business software, but I dont know the performance of SGI's first(?) scale-up server. Anyway, 16 socket servers are different from SGI UV2000 scale out clusters. And UV2000 can not be used for business software. As evidenced by non existing SAP benchmarks.
    Reply
  • ats - Wednesday, May 13, 2015 - link

    No, you haven't shown anything. You quote some random whitepaper on the internet like it is gospel and ignore the fact that in memory dbs are used daily as the primary in OLTP, OLAP, BI, etc workloads.

    And you don't understand that a significant number of the IMDBs are actually designed directly for the OLTP market which is precisely the DB workload that is modifying the most data and is the most complex and demanding with regard to locks and updates.

    There is no architecural difference between the UV300 and the UV2k except slightly faster interconnect. And just an fyi, UV300 is like SGI's 30th scale up server. After all, they've been making scale up server for longer than Sun/Oracle.
    Reply
  • questionlp - Monday, May 11, 2015 - link

    HP Superdome X is a 16-socket x86 server that will probably end up replacing the Itanium-based Superdome if HP can scale the S/X to 32 sockets. Reply
  • Brutalizer - Monday, May 11, 2015 - link

    HP will face great difficulties if they try to mod and go beyond 8 sockets on the old Superdome. Heck, even 8 sockets have scaling difficulties on x86. Reply
  • Kevin G - Monday, May 11, 2015 - link

    Except that you can you buy a 16 socket Superdome X *today*.

    http://h20195.www2.hp.com/V2/getpdf.aspx/4AA5-6149...

    The interconnect they're using for the Superdome X is from the old Poulson Itaniums that use QPI which can scale to 64 sockets.
    Reply
  • rbanffy - Wednesday, May 13, 2015 - link

    You talk "serious business workloads". Of course, there are organizations that use technology that does not scale horizontally, where adding more machines to share the workload does not work because the workload was not designed to be shared. For those, there are solutions that offer progressively less performance per dollar for levels of single-box performance that are unattainable on high-end x86 machines, but that is just because those organizations are limited by the technology they chose.

    There is nothing in SAP (except its design) or (non-rel) databases that preclude horizontal scaling. It's just that the software was designed in an age when horizontal scaling was not in fashion (even though VAXes have been doing clustering since I was a young boy) and now it's too late to rebuild it from scratch.
    Reply
  • mapesdhs - Friday, May 8, 2015 - link

    Good point, I wonder why they've left it at only 2/core for so long... Reply
  • name99 - Friday, May 8, 2015 - link

    It's not easy to ramp up the number of threads. In particular POWER8 uses something I've never seen any other CPU do --- they have a second tier register file (basically an L2 for registers) and the system dynamically moves data between the two register files as appropriate.

    It's also much easier for POWER8 to decode 8 instructions per cycle (and to do the multiple branch prediction per cycle to make that happen). Intel could maybe do that if they reverted to a trace cache, but the target codes for this type of CPU are characterized by very large I-footprints and not much tight looping, so trace caches, loop caches, micro-op caches are not that much help. Intel might have to do something like a dual-ported I-cache, and running two fetch streams into two independent sets of 4-wide decoders.
    Reply
  • xdrol - Saturday, May 9, 2015 - link

    Another register file is just a drop in the ocean. The real problem is the increasing L1/2/.. cache pressure; what can only be mitigated by increasing cache size; what in turn will make your cache access slower, even when you use only one of the SMT threads.

    Also, you need to have enough unused execution capacity (pipeline ports) for another hardware thread to be useful; the 2 threads in Haswell can already saturate the 7 execution ports with quite high probability, so the extra thread can only run in expense of the other, and due to the cache effects, it's probably faster to just get the 2 tasks executed sequentially (within the same thread). This question could be revisited if the processor has 14 execution port, 2x issue, 2x cache, 2x everything, so it can have 4T/1C, but then it's not really different from 2 normal size cores with 4T..
    Reply
  • iAPX - Friday, May 8, 2015 - link

    It's because this is the same architecture (mainly) that is used on desktop, laptops, and now even mobility!

    With this market share, I won't be surprised that Intel decided to create a new architecture (x86-64 based) for future server chips, much more specialized, dropping AVX for cloud servers, having 4+ threads per core with simpler decoder and a lot of integer and load/store units!

    That might be complemented by a Xeon Phi socketable for floating-point compute intensive tasks and workstations, but it's unclear even if Intel announced it far far ago! ;)
    Reply

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