On Thursday, April 23, 2015 at 10:14:01 PM UTC-4, Gabriel Hackebeil wrote: > > I've run the benchmark tests after compiling Crypto++ 5.6.2 with the > latest versions of the Intel compilers (icpc 15.0.2), GNU g++ (4.9 and > 5.1), and Clang (Apple LLVM version 6.1.0). I'm basically interested in > getting the best possible performance for AES in CTR mode, and the results > of the benchmarks were surprising. In my limited understanding, use of the > AES-NI instruction set (which I believe only the Intel compiler can > utilize) is supposed to provide a big performance boost for AES. The > results do not show this. For the AES mode of interest (CTR), the > throughput I achieve (as reported by the benchmark test suite) is roughly: > > Clang: ~1 GiB/second > Intel: ~1.7 GiB/second > GNU: ~4.1 GiB/second > > Can someone explain why GNU has such a huge boost in performance (~2.5x) > over Intel, when GNU can not use the AES-NI instructions (I don't care much > about Clang)? I get the same results comparing Intel and GNU on a Linux VM. > Let me know if you need any relevant machine specs (Intel core i7 cpu). The > relevant compiler flags appearing on Linux vs OS X are shown below (the > performance results are the same on either operation system and I've played > with various optimization flags for each without much change in > performance). Can anyone enlighten me about the lack of performance boost > from AES-NI? >
It may depend on your processor. Are you using an Intel processor, or an AMD (or other) processor. Intel has been known to do sneaky things, like provide sub-optimal code on non-Intel processors. Way back when when Intel was caught doing this, they did not stop doing it. Rather, they informed developers they were doing it to side step consumer protection laws. See, for example, http://www.agner.org/optimize/blog/read.php?i=49#49 or https://www.google.com/search?q=intel+bad+code+on+amd. -- -- You received this message because you are subscribed to the "Crypto++ Users" Google Group. To unsubscribe, send an email to [email protected]. More information about Crypto++ and this group is available at http://www.cryptopp.com. --- You received this message because you are subscribed to the Google Groups "Crypto++ Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
