RFR: 8361076: Add benchmark for ImageReader in preparation for Valhalla changes [v2]

[David Beaumont]

On Mon, 30 Jun 2025 13:18:19 GMT, David Beaumont <duke at openjdk.org> wrote:

>> Initial benchmark to capture at least some comparative measures of ImageReader performance.
>> 
>> Current results on my laptop:
>> 
>> Benchmark                                         Mode  Cnt   Score    Error  Units
>> NewImageBenchmark.warmCache_CountAllNodes         avgt    5   0.785 ±  0.140  ms/op
>> NewImageBenchmark.coldStart_CountOnly               ss    5  34.051 ± 17.662  ms/op
>> NewImageBenchmark.coldStart_InitAndCount            ss    5  31.006 ±  9.674  ms/op
>> NewImageBenchmark.coldStart_LoadJavacInitClasses    ss    5   3.752 ±  6.873  ms/op
>> 
>> The upcoming changes to ImageReader should show significant improvements to these results.
>
> David Beaumont has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Renaming class.

test/micro/org/openjdk/bench/jdk/internal/jrtfs/NewImageBenchmark.java line 71:

> 69:     }
> 70: 
> 71:     /// NOT a @State since that causes setUp()/tearDown() to be shared, but we

This comment might have been before I applied `Scope.Benchmark` to the states below. I'll double check if it's still an issue.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26044#discussion_r2175050289