RFR: 8308118: Avoid multiarray allocations in AESCrypt.makeSessionKey [v2]

[Aleksey Shipilev]

On Tue, 16 May 2023 09:18:57 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> One of our services has a hot path with AES/GCM cipher reuse. The JDK code reinitializes the session key on that path, and [JDK-8308105](https://bugs.openjdk.org/browse/JDK-8308105) shows up prominently there.
>> 
>> Fixing [JDK-8308105](https://bugs.openjdk.org/browse/JDK-8308105) would take a while, as would likely require multiple patches in VM internals. Meanwhile, we can avoid the multiarray allocations in AESCrypt.makeSessionKey completely, reaping performance benefits. We can go even deeper: replace the multi-array with the flat array and drop `expandToSubKey` completely.
>> 
>> Example original profile is in the bug.
>> 
>> There are other things we can polish in that code, but experiments show those polishings have rather diminshed returns.
>> 
>> On new benchmark:
>> 
>> 
>> Benchmark       Mode  Cnt    Score   Error  Units
>> 
>> ## Mac M1
>> 
>> # Before
>> AESReinit.test  avgt   15   873,842 ± 6,911  ns/op
>> 
>> # After
>> AESReinit.test  avgt   15   347,632 ± 8,764  ns/op  ; <--- 2.5x faster
>> 
>> ## Xeon, c6.8xlarge
>> 
>> # Before
>> AESReinit.test  avgt   15  1524.307 ± 24.231 ns/op
>> 
>> # After
>> AESReinit.test  avgt   15   554.727 ± 12.876 ns/op  ; <--- 2.75x faster
>> 
>> ## Graviton, m6g.4xlarge
>> 
>> # Before
>> AESReinit.test  avgt   15  1913.492 ± 23.489 ns/op
>> 
>> # After
>> AESReinit.test  avgt   15   639.701 ± 5.033  ns/op  ; <--- 2.99x faster
>> 
>> 
>> Additional testing:
>>  - [x] Benchmarks
>>  - [x] macos-aarch64-server-release, `jdk_security`
>>  - [x] linux-x86_64-server-fastdebug, `tier1 tier2 tier3`
>
> Aleksey Shipilev has updated the pull request incrementally with three additional commits since the last revision:
> 
>  - Micro-optimizations
>  - Handle Kd
>  - Handle Ke

Rechecked `jdk_security`, passes. Thanks!

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PR Comment: https://git.openjdk.org/jdk/pull/13996#issuecomment-1554093536