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  1. JDK
  2. JDK-8260337

Optimize ImageReader lookup, used by Class.getResource

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    • b09

    Description

      As a proxy for a resource lookup, consider String.class.getResource("String.class"). This will drop into the jimage code reading lib/modules to produce a URL to the String.class bytes.

      A microbenchmark shows just getting to that URL is quite costly:

      Benchmark Mode Cnt Score Error Units
      ClassGetResource.stringClass avgt 5 2885.403 ± 309.787 ns/op
      ClassGetResource.stringClass:·gc.alloc.rate.norm avgt 5 1368.124 ± 0.056 B/op

      There are several inefficiencies along this path that could be addressed, including adding an ASCII fast-path to the jimage verification code that checks if the name points to a real resource.

      Optimizing the underlying jimage code can be helpful for a variety of applications, including javac.

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              redestad Claes Redestad
              redestad Claes Redestad
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