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

Vicente Romero vromero at openjdk.java.net
Thu Oct 22 02:09:12 UTC 2020

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