RFR: 8295010: Reduce if required in EC limbs operations [v5]

[Xue-Lei Andrew Fan]

On Tue, 29 Nov 2022 18:38:34 GMT, Sean Mullan <mullan at openjdk.org> wrote:

>>> I may run it again after the integration of multiplicative inversion and point multiplication improvement.
>> 
>> After the integration of the improvement above, here is the benchmark numbers with this patch:
>> 
>> Benchmark                    (algorithm)  (messageLength)   Mode  Cnt     Score     Error  Units
>> Signatures.EdDSA.sign            Ed25519               64  thrpt   15  1084.556 ± 135.637  ops/s
>> Signatures.EdDSA.sign            Ed25519              512  thrpt   15  1168.663 ±  25.072  ops/s
>> Signatures.EdDSA.sign            Ed25519             2048  thrpt   15  1186.863 ±  16.224  ops/s
>> Signatures.EdDSA.sign            Ed25519            16384  thrpt   15  1095.034 ±   6.462  ops/s
>> Signatures.EdDSA.sign              Ed448               64  thrpt   15   323.771 ±   2.156  ops/s
>> Signatures.EdDSA.sign              Ed448              512  thrpt   15   326.995 ±   2.101  ops/s
>> Signatures.EdDSA.sign              Ed448             2048  thrpt   15   320.799 ±   5.452  ops/s
>> Signatures.EdDSA.sign              Ed448            16384  thrpt   15   317.715 ±   2.554  ops/s
>> Signatures.sign                secp256r1               64  thrpt   15  4072.636 ±  22.441  ops/s
>> Signatures.sign                secp256r1              512  thrpt   15  4048.822 ±  40.769  ops/s
>> Signatures.sign                secp256r1             2048  thrpt   15  4042.884 ±  20.147  ops/s
>> Signatures.sign                secp256r1            16384  thrpt   15  3911.856 ±  12.039  ops/s
>> Signatures.sign                secp384r1               64  thrpt   15   634.203 ±   4.532  ops/s
>> Signatures.sign                secp384r1              512  thrpt   15   637.623 ±   1.592  ops/s
>> Signatures.sign                secp384r1             2048  thrpt   15   620.283 ±  10.014  ops/s
>> Signatures.sign                secp384r1            16384  thrpt   15   622.617 ±   5.695  ops/s
>> Signatures.sign                secp521r1               64  thrpt   15   311.957 ±   5.420  ops/s
>> Signatures.sign                secp521r1              512  thrpt   15   316.605 ±   2.204  ops/s
>> Signatures.sign                secp521r1             2048  thrpt   15   316.700 ±   1.654  ops/s
>> Signatures.sign                secp521r1            16384  thrpt   15   309.599 ±   7.167  ops/s
>> 
>> 
>> and the numbers without this patch:
>> 
>> Benchmark                    (algorithm)  (messageLength)   Mode  Cnt     Score     Error  Units
>> Signatures.EdDSA.sign            Ed25519               64  thrpt   15  1138.578 ±  57.908  ops/s
>> Signatures.EdDSA.sign            Ed25519              512  thrpt   15  1172.242 ±  17.180  ops/s
>> Signatures.EdDSA.sign            Ed25519             2048  thrpt   15  1163.793 ±  21.095  ops/s
>> Signatures.EdDSA.sign            Ed25519            16384  thrpt   15  1093.856 ±   5.964  ops/s
>> Signatures.EdDSA.sign              Ed448               64  thrpt   15   324.089 ±   2.894  ops/s
>> Signatures.EdDSA.sign              Ed448              512  thrpt   15   323.580 ±   1.437  ops/s
>> Signatures.EdDSA.sign              Ed448             2048  thrpt   15   323.680 ±   2.555  ops/s
>> Signatures.EdDSA.sign              Ed448            16384  thrpt   15   310.641 ±   2.256  ops/s
>> Signatures.sign                secp256r1               64  thrpt   15  4070.733 ±  27.059  ops/s
>> Signatures.sign                secp256r1              512  thrpt   15  4061.835 ±  18.776  ops/s
>> Signatures.sign                secp256r1             2048  thrpt   15  4041.226 ±  19.082  ops/s
>> Signatures.sign                secp256r1            16384  thrpt   15  3893.323 ±  11.869  ops/s
>> Signatures.sign                secp384r1               64  thrpt   15   632.924 ±   8.273  ops/s
>> Signatures.sign                secp384r1              512  thrpt   15   628.807 ±   7.604  ops/s
>> Signatures.sign                secp384r1             2048  thrpt   15   631.052 ±   1.782  ops/s
>> Signatures.sign                secp384r1            16384  thrpt   15   530.402 ± 122.967  ops/s
>> Signatures.sign                secp521r1               64  thrpt   15   316.634 ±   1.724  ops/s
>> Signatures.sign                secp521r1              512  thrpt   15   315.830 ±   2.333  ops/s
>> Signatures.sign                secp521r1             2048  thrpt   15   315.855 ±   1.093  ops/s
>> Signatures.sign                secp521r1            16384  thrpt   15   315.019 ±   1.124  ops/s
>
> @XueleiFan, I have some questions about this integration. The performance numbers you last posted showed some very small improvements but also some regressions in throughput numbers, so its not clear to me if this is worth integrating yet. Earlier, you said that the performance benefits of this fix would not be realized until the changes for https://github.com/openjdk/jdk/pull/10398 were to be integrated, but that change is still in draft and has comments that have not been resolved. So, is it possible this was integrated too early?

@seanjmullan if you check the benchmark numbers, the throughput impact is limited.  For some curves, it is improved; and some others is impacted.  In theory of this update, it is not expected to have performance impact if no improvement.  The throughput impact in the benchmark is more from the noice in the benchmark platform, I think.

The fix for [10398](https://github.com/openjdk/jdk/pull/10398) depends on this update.  Only after integrating this one, I can open  [10398](https://github.com/openjdk/jdk/pull/10398) for review.  The code is ready for  [10398](https://github.com/openjdk/jdk/pull/10398) , I'm running the benchmarking.  Once the benchmark numbers are ready, I will open it for review.  It should be ready to review today.

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

PR: https://git.openjdk.org/jdk/pull/10624