RFR: 8269404: Base64 Encoding optimization enhancements for x86 using AVX-512

[Scott Gibbons]

On Sat, 26 Jun 2021 15:07:43 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Enhance the Base64 Encode intrinsic for x86 using AVX-512 to get better performance. Also allow for performance improvement on non-AVX-512 enabled platforms.
>> 
>> Added AVX-512 code for encoding Base64 blocks, including slight improvements for non-AVX-512 x86 platforms.
>> 
>> Running the Base64Decode benchmark, this change increases decode performance by an average of 2.6x with a maximum 9.7x for buffers > ~20k.  The numbers are given in the table below.
>> 
>> **Base Score** is without intrinsic support, **Optimized Score** is using this intrinsic, and **Gain** is **Base** / **Optimized**.
>> 
>> Benchmark Name | Base Score | Optimized Score | Gain
>> -- | -- | -- | --
>> testBase64Encode size 1 | 8.10 | 8.04 | 1.01
>> testBase64Encode size 2 | 8.51 | 8.43 | 1.01
>> testBase64Encode size 3 | 11.08 | 10.72 | 1.03
>> testBase64Encode size 6 | 13.98 | 13.12 | 1.07
>> testBase64Encode size 7 | 14.44 | 13.38 | 1.08
>> testBase64Encode size 9 | 15.44 | 14.37 | 1.07
>> testBase64Encode size 10 | 16.13 | 14.97 | 1.08
>> testBase64Encode size 48 | 27.14 | 23.23 | 1.17
>> testBase64Encode size 512 | 123.86 | 30.75 | 4.03
>> testBase64Encode size 1000 | 224.42 | 37.71 | 5.95
>> testBase64Encode size 20000 | 4202.11 | 430.16 | 9.77
>
> @asgibbons if you are still working on this, please convert it to `draft` PR. There is `Convert to draft` link under `Reviewers`:
> 
> Reviewers
> No reviews
> Still in progress? Convert to draft
> 
> Otherwise it seems like it is ready for review and we got RFR emails.

Thanks, @vnkozlov.  I have tested this on all the platforms I have available to me, and it has been internally reviewed.  I'm a novice when it comes to this process and I have read the contributing guidelines, but I'm at a loss as to how draft PRs are used.

I believe this is the change that will ultimately be integrated, so in fact I am looking for reviews.  Can you enlighten me please?

-------------

PR: https://git.openjdk.java.net/jdk/pull/4601