Re: [dpdk-dev] [PATCH v2 03/12] crypto/armv8: Add core crypto operations for ARMv8

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

On Tue, Dec 06, 2016 at 10:42:51PM +0100, Thomas Monjalon wrote:
> 2016-12-07 02:48, Jerin Jacob:
> > On Tue, Dec 06, 2016 at 09:29:25PM +0100, Thomas Monjalon wrote:
> > > 2016-12-06 18:32, zbigniew.bodek@caviumnetworks.com:
> > > > From: Zbigniew Bodek <zbigniew.bodek@caviumnetworks.com>
> > > > 
> > > > This patch adds core low-level crypto operations
> > > > for ARMv8 processors. The assembly code is a base
> > > > for an optimized PMD and is currently excluded
> > > > from the build.
> > > 
> > > It's a bit sad that you cannot achieve the same performance with
> > > C code and a good compiler.
> > > Have you tried it? How much is the difference?
> > 
> > Like AES-NI on IA side(exposed as separate PMD in dpdk),
> > armv8 has special dedicated instructions for crypto operation using SIMD.
> > This patch is using the "dedicated" armv8 crypto instructions and SIMD
> > operation to achieve better performance.
> 
> It does not justify to have all the code in asm.

Why ? if we can have separate dpdk pmd for AES-NI on IA . Why not for ARM?

> 
> > We had compared with openssl implementation.Here is the performance
> > improvement for chained crypto operations case WRT openssl pmd
> > 
> > Buffer
> > Size(B)   OPS(M)      Throughput(Gbps)
> > 64        729 %        742 %
> > 128       577 %        592 %
> > 256       483 %        476 %
> > 512       336 %        351 %
> > 768       300 %        286 %
> > 1024      263 %        250 %
> > 1280      225 %        229 %
> > 1536      214 %        213 %
> > 1792      186 %        203 %
> > 2048      200 %        193 %
> 
> OK but what is the performance difference between this asm code
> and a C equivalent?

Do you you want compare against the scalar version of C code? its not
even worth to think about it. The vector version will use
dedicated armv8 instruction for crypto so its not portable anyway.
We would like to asm code so that we can have better control on what we do
and we cant rely compiler for that.