RFR: 8270091: The path of JFR emergency dump should be able to specified by the user

[Yasumasa Suenaga]

On Thu, 8 Jul 2021 12:29:03 GMT, Yasumasa Suenaga <ysuenaga at openjdk.org> wrote:

> JFR will dump the recording to the file as hs_err_pid<PID>.jfr if JVM encountered fatal errors (e.g. crash). It will be dumped to current directory, and we cannot specify dump path.
> 
> In other dumps (hs_err log, heap dump, replay & inline data for JIT) can be specified it.
> 
> This is useful especially in the container application if we can specify it in JFR.
> 
> I've filed [CSR](https://bugs.openjdk.java.net/browse/JDK-8270093) for this RFE, please review it too.

I tested to set `dumppath` via `JFR.configure` dcmd, but it did not affect. Emergency dump (hs_err_pid1046.jfr) was dumped to current directory.
(I use https://github.com/YaSuenag/garakuta/tree/master/NativeSEGV to happen the crash)

### Terminal 1


$ java -Djava.library.path=. -jar NativeSEGV.jar -s


### Terminal 2


$ jcmd 1046 JFR.configure dumppath=/tmp
1046:
Dump path: /tmp

$ jcmd 1046 JFR.start
1046:
Started recording 1. No limit specified, using maxsize=250MB as default.

Use jcmd 1046 JFR.dump name=1 filename=FILEPATH to copy recording data to file.

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PR: https://git.openjdk.java.net/jdk/pull/4724