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

[Erik Gahlin]

On Tue, 3 Aug 2021 02:31:01 GMT, Yasumasa Suenaga <ysuenaga at openjdk.org> wrote:

> 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.
> ```

It's a bug. 

When it comes to filename, It's fine to implement it, but it would be good to first discuss the design.

-------------

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