RFR: 8254723: add diagnostic command to write Linux perf map file [v2]

[Vicente Romero]

On Thu, 22 Oct 2020 01:24:20 GMT, Yasumasa Suenaga <ysuenaga at openjdk.org> wrote:

>>> 
>>> Because it seems that for the short jobs, we would like to just do "perf record java -XX:+WhatEver", followed by "perf report", without requiring user to invoke the diagnostic command while JVM is still running?
>> 
>> Yes that sounds like a good idea. Add a (diagnostic?) option `-XX:+WritePerfMapOnExit`?
>
>> Yes that sounds like a good idea. Add a (diagnostic?) option `-XX:+WritePerfMapOnExit`?
> 
> I think we should use this option carefully because nmethod might be unloaded. So we should use this with `-XX:-UseCodeCacheFlushing`.
> 
> BTW we can use `Compiler.codelist` dcmd for this purpose now. If you implement `WritePerfMapOnExit`, we should consider code cache flushing and should use `Compiler.codelist` in some case. I've published perfmap generator from `Compiler.codelist` https://github.com/YaSuenag/saperf

\label remove compiler

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PR: https://git.openjdk.java.net/jdk/pull/760