[openssl-users] BN_MUL_MONT for ARM64 v8

[Mike Mohr]

Have you considered using GMP as a big integer backed for openssl?  It has
support for several arm variants using handwritten assembly code and the
developers go to great lengths to find optimize runtime on all supported
platforms.

On Feb 7, 2017 2:26 PM, "Vijay Chander" <vijay.chander at gmail.com> wrote:

Andy,
   1:2.5 is pretty in my opinion for ARM !

   We  will check out Mongoose.

   Hmm - will try to get to the bottom of those cache misses (at a lower
priority).

Thanks,
-vijay



On Tue, Feb 7, 2017 at 11:07 AM, Andy Polyakov <appro at openssl.org> wrote:

> > A72 is running 1GHz compared to x86 at 2.1Ghz. So that should hopefully
> > get down to -1:5.
>
> And Mongoose will take you to ~1:2.5 (scaled to same frequency that is).
> Which I'd say is a fair result. Well, still could have been a bit
> better, but it's not unreasonable given ISA differences. Keep in mind
> that presented x86_64 result is for code utilizing Intel-specific code
> extensions.
>
> > There is no L3 cache on the A72 eval board and performance counters do
> > show 9x more DRAM accesses for ARM compared to x86.
>
> This is unexpected, because it takes *less* references to memory to
> perform it on ARMv8. Because it has larger register bank. And cache
> requirement is not that high for L3 to kick in... But at any case memory
> is not bottleneck here...
>
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