RFR: 8340571: Outline code from the loop in ZipFile.Source.initCen [v3]

[Claes Redestad]

On Wed, 25 Sep 2024 13:43:49 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> This PR suggests refactoring `ZipFile.Source.initCEN` to move as much logic as possible into the per-entry method processor. This inner method will be called often and JIT optimized earlier in the bootstrap sequence.
>> 
>> Startup tests using the OpenJDK benchmarks.jar show a ~1ms improvement on both my M1 macbook and my x64 wokstation, while we also improve on relevant throughput microbenchmarks:
>> 
>> 
>> Name               (size) Cnt       Base      Error        Test      Error  Unit  Change
>> openCloseZipFile      512  15  61372.449 ± 1197.432   58081.423 ± 1751.988 ns/op   1.06x (p = 0.000*)
>> openCloseZipFile     1024  15 117953.727 ± 3202.274  112548.875 ± 5126.665 ns/op   1.05x (p = 0.001*)
>> openCloseZipFilex2    512  15  62141.795 ±  674.121   60520.017 ± 2438.346 ns/op   1.03x (p = 0.017 )
>> openCloseZipFilex2   1024  15 117959.071 ± 1528.426  111773.937 ± 1604.412 ns/op   1.06x (p = 0.000*)
>>   * = significant
>
> Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Typo

Worth trying out. Your approach seem to improve on throughput, while my main goal has been improving on startup/warmup with throughput wins as a side effect. Let's get #20905 reviewed and integrated, sync up then I'll play around with some variants here. I'll put this back as draft in the interim.

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PR Comment: https://git.openjdk.org/jdk/pull/21133#issuecomment-2374984794