RFR: Adding troubleshooting section to README.md

[Maurizio Cimadamore]

On Mon, 25 Jan 2021 10:13:25 GMT, Adam Sotona <asotona at openjdk.org> wrote:

> Hi,
> based on an external contributor recent experience with javac benchmarking javac using jmh-jdk-microbenchmarks I've created a troubleshooting section of the README.md
> 
> Thanks,
> Adam

Looks a good troubleshooting guide. I've left some comments

README.md line 72:

> 70: 
> 71: micros-javac benchmarks consist of two sets of benchmarks: 
> 72:  * `SingleJavacBenchmark` (which is parametrized) measures each single javac compilation stage in an isolated run. This benchmark is designed for exact automated performance regression testing and it takes several ours to execute completely. 

Suggestion:

 * `SingleJavacBenchmark` (which is parametrized) measures each single javac compilation stage in an isolated run. This benchmark is designed for exact automated performance regression testing and it takes several hours to execute completely.

README.md line 60:

> 58: It is caused by recently enabled Jigsaw enforcement and micros-javac benchmarks requirement to access several jdk.compiler module private packages. 
> 59: 
> 60: Solution is to export required packages by adding following options to the command line:

assuming this issue comes from reflective access, what about adding a single option to permit illegal access?

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PR: https://git.openjdk.java.net/jmh-jdk-microbenchmarks/pull/5